A833 In Truck
I have a bell from a 69-71? 340. Would that work
Maybe... ?
The 3515734 has the same side bolt hole arrangement as the 1975-'80 overdrive bellhousing, so the truck's ball stud bolts into the same location on both bells. The ball stud bolt holes are located differently on the 2892482 bellhousing so the countershaft alignment would be off. It might still work with a tilted countershaft, but I honestly don't know. I do know one person using the '69-'71 car A-body stud on the OD bell with mildly compromised angles, but it works. However, that's in a Dart--an entirely different ball of wax than the truck part.
If you already had the parts lying around, I'd say try it. But you need the truck ball stud, which it doesn't sound like you have, and I'm not one to advise spending money on "maybe you could cobble it together". The 734 and 482 bellhousings are of approximately equal value, so you might be able to work out a trade with someone.
However, as noted above,
neither of those bellhousings will work with an actual Road Runner transmission, which would have a 4.80" bearing retainer. No factory small-block bellhousing used that size. They were either 4.35" or 5.125" (overdrive only). Road Runners didn't get small-blocks until 1971, and a RR transmission from '71 or later would have the rear shifter mount location missing from the one in your picture.