I won an Intermountain F3A and F3B units from eBay. They arrived with some shipping damage, broken couplers on the B ends. Going to Micro Trains site, it says F3 came “Pre equipted w/MT” not much help. Looking at the list for FT I find “1023 (001 02 009) front of A unit and 1015 (001 02 000) rear of B” So I assume 1015 will work on the F3A and B rear?
To me it would depend on the coupled distance and whether or not these units will be uncoupled. I use Unimates between units in all my ABBA lashups. They run as a unit and I never uncouple them. Added plus is they couple very close, closer than MT's and look a lot better.
I just got several packs of the "new" body mounts that are made by Fox Valley (formally Unimates) for my ABBA's. If you want to maintain the MT's, they used 1015-1016's on them.
I equipped all my Intermountain 'F' units with Unimates. I always run the Intermountain "F" units in an "A-B-B-A" arrangement. They never get broken up. The Unimates keep all four units close coupled. Have fun with it.... Shades
The body mounts have holes for screws. I think when I did my last set, I used a 1/4" long oo-90 screw as the ones that hold the MT's on is a little too long