If you are doing a serious restoration, here are a couple of basic tips and repro part differences that you should be aware of: 

TR3's

Front Bumper - The repro bumpers which are currently available have a flare on either end and don't "fit" exactly the same way as the original. If you look at 2 cars side by side there is a noticeable difference as the repro flares outward on either end.

Door pulls - Door pulls are supplied as bicycle cables ...... save yourself the cost of a special order and just get a length of black bicycle cable (with a lead stop on both ends) and cut to size - a 5 or 6 ft cable is sufficient for both doors

Front Grill - the repro front grill has a duller finish than an original grill. Originals are chromed aluminum. Original grills are very hard to come by but if you do have an original grill try to straighten it out and salvage it

Lift the dot studs - The original small male studs are slightly different than the repro. If you have original studs try to have them re-chromed, if not order replacements from Roadster factory as theirs are the next best thing. Same applies for the windscreen studs

 Flasher units - These cars use a different flasher unit that what you will find in most autoparts stores. Heavy duty Triton units will work fine if you can find them.

General to all models

Water pump - The original water pump is no longer available and the repro pump does not have a grease fitting as the sealed bearings don't require it to be greased. The body of the new pump casting is more "beefy" on the flanges and is slightly different on the front face. There is some extra metal on the casting which will interfere with the rotation of the old style pulley, so you will have to grind down a small amount bit of casting if using an old pulley with a repro pump. Tip: Some folks will drill and tap a hole in the new style repro pump and install the grease zerk. If you do that the new and old style pumps are almost indistinguishable to the discerning eye.

Lift the dot snaps - these should run vertically on your tops and tonneau's with the narrow end pointed upwards

Interior kits - Kits are available in many color combinations but may not be correct for your year and model. If you are replacing an interior and wish to go to a different color, make sure that it was originally available for that year.

Carpet sets - The original cars came with a simple loop pile carpet. Many parts suppliers offer better quality carpet sets. If you want original stick with simple. Originally they covered the area behind the seats, under the seats and the tunnel. The floor in front of the seats was covered with a rubber mat which extended up onto the firewall about a foot, and were secured by two clips at the top. The rubber mat covers the edges of the tunnel carpet.

Trunk carpet kits - these are great to have to protect your trunk but don't glue them in place if you are planning to show the car. The only thing that should be in there is the "Hardura" trunk floor mat

Exterior paint colors - If you are repainting your car, there is nothing wrong with changing the color, but try to stick with an originally available color. Many colors were not available in any given year so you should consult Bill Piggots "Original TR 2/3/3A" for what was offered and make sure it also goes with the then available interior color. Original paint on these cars was Enamel which cracked after 5-10 years so you are much better off painting your car with a modern day durable type clearcoat paint.

Screws - All screws are slotted type except those that hold the front grill in place. Don't order a bunch of screws and small hardware items from the parts suppliers, you will pay 5 or 10 times what the item will cost you at a local Home Depot. (Same applies on bolts and nuts)

Bolts and nuts - with the exception of motor bolts, all bolts are fine thread imperial type. Remember to use grade 5 bolts on all steering and suspension components!

Grommets - Again you will find most of what you need at Home Depot. The part suppliers charge a small fortune for these simple items

Rebuilding carburetors, brake cylinders and shock absorbers - This is best left up to professionals unless you know what you are doing. Apple Hydraulics in NY state does them all

Motor head rebuilds - When rebuilding plan on installing hardened "stelite" faced valves with Silicone -bronze guides and hardened exhaust seats. This will allow you to skip having to add a lead additive with every tank of gas.

Gas and brake lines - If you know what you are doing, get a small pipe bender, cutter and a double flaring kit and make your own lines. Brake lines are 1/8 ID pipe, (pipes to master cylinders are 3/16') fuel lines are 1/4". Make sure to double flare all ends and use white silicone sealant on threads to prevent leaks and TIGHTEN UP THOSE FITTINGS. Nothing more heartbreaking than finding brake fluid leaking on fresh paint. Rubber hoses for gas lines connections are 1/4" ID.

Rebuilt gauges - Nissinger is probably the best rebuilder of gauges

These repair and tip manuals were written by A. Rohdes:
Repairing Smith/Jaeger Speedometers
Adjusting Armstrong lever shocks
Generator/Voltage regulator adjustment 
Camshaft discussion

Please feel free to e-mail me any tips which you would like to pass on to other restorers. jacad@videotron.ca