The new trucks should be just fine. The screws have changed from slotted to Phillips, not an issue.
I haven’t seen the really old kits, but I wouldn’t think they wouldn’t be too difficult to assemble. I imagine they’re much like Athearn’s old blue box line in HO. “Shake the box”, ie. attach a few parts to the main body. May require some glue, but not much.
Depending on what type of car it is, add weight beyond what is supplied. Weavers are grossly under weighted when the NMRA recommended practice is applied.
That rule is: 5oz + 1oz per inch of actual car length.
Depends on the kit[:D] in the 70s Weaver cars were Craftsman kits, meaning a box of sticks. Early 80s, was when Bob Weaver came out with his 2 bay hopper.
I run weaver cars on my 2 rail layout, excellent cars, good price, and great workmanship (Made in Pa [:D][:D][:D][:D][:D]) One of the best features is convertability. A 3 rail car can be made 2 rail by changing trucks, adding Kadee couplers (for long trains, or locomotives, Weaver scale couplers are too weak. Makes train handling real important!) and going for it!
As for the weight issue, I run a ounce per inch, not five ounces per inch. At five ounces, the train weights will be way too high, causing excessive amp draw, and heating issues on locomotives and power supplies!
Remember, the Weaver cars are full scale, so, some may look out of place when ran with traditional O gauge size cars.
You misunderstood the weighting. It means 5oz for the car as a base plus 1oz per inch.
The formula is X + 5, where X is the length of the car.
An ACF 4 bay hopper is 14" long. 14 + 5 = 19oz.
One oz per inch is probably OK for most “toy” trains, which have the advantage of oversized flanges. However, if you have tight curves, and plan to run long trains or do any backing up, you might find the extra 5oz helpful in keeping your trains on the track. I didn’t make this up, the NMRA did.[;)]