Older Intermountain Kits, 3 Rail Upgrade?

 They did sell some of these ready to go for 3 rail. They used Weaver trucks. They used a bonded washer to raise the height of the car to gain clearance for the truck to pivot. The Atlas truck would probably need a lot more work to mount. The height is much lower than the Weaver. Weaver trucks are scarce if you are looking for the diecast ones. Anything is do able. Factor in the cost of the car and buying the trucks. Then price out old Atlas stock. Atlas re did some Intermountain cars in their Masterline. With Atlas you get the added benefit of a die cast chassis and a more rugged car. The Atlas detail as fragile as it may seem. Is more durable than Intermountains.

 If you want to go the easiest and least costly route. I would use Weaver's plastic trucks. You should be able to come up with the trucks at a good price. Many upgraded their cars  to diecast. Their should be a surplus of the plastic ones around. A lot of guys adding Kadee's to Weavers. I was pretty much giving away die cast couplers.

The kits are cheap for a reason. Yes they have a lot of detail but are fragile and take time to build. Make sure you add some weight to them before you glue them all together. Like previously mentioned, you have to figure the price of new trucks/wheel sets into the price of the car. I think you'll find you will still have $40-$50 in each car PLUS all the time to build & convert them to 3 rail.

All of the Intermountain O scale KITS I have built and have yet to build come with both 2 rail and 3 rail trucks. Maybe some of the earliest ones did not but I have not come across any that did not. The ready to run versions came with either two rail or three rail trucks but not both. If you want to run on three rail some of the underbody detail like brake lines and hoses will have to left off or the wheel flanges and couplers will limit turning.

Back in the early '90s K-Line had Intermountain make a line of scale reefers for them. These came with diecast trucks but minimal underbody detail. 

BTW the reason the prices may seem low is because few O scalers like to build kits any more. Few pieces of rolling stock can match their detail including brass. Yes its very delicate and its not for the person who is constantly handling their rolling stock but for those who just leave them on the layout and run them.

Pete

If you can find them. There are 3r upgrade kits for Intermountain. I have 7 kits. It contains Dummy claw and high rail wheel sets. The claw snaps right on the trucks. Atlas trucks will work. You just need not attach the bolsters when assembling the kit. Weaver trucks are the best if you can find them.  Also if the kits are complete. They will come with the high rail wheel sets and couplers. Your just going to have to open to Make sure kit is complete. I will post pics later as I getting the the kids ready for school.