Re: Looking for some motor input.
The later 460s still had a lot of potential
What I would do first, is swap the timing set for an earlier version. Unfortunately it's not easy to tell what is in there now, so buying one for say a 69 429/460 from a reputable company that lists a different part number for a 1977 460 should get you there. If you consider it, post part numbers here and we'll check
Your comment that you do not rev it high is fine, actually better, the later timing sets retard the cam timing for emissions, what that does is shift the torque curve higher, so by advancing the cam you gain vacuum and torque, and overall the engines run better
In addition, while it is apart I would consider having the distributor recurved, there are 460 guys around that can give common standards for stock motors, but I would shoot for 12 degrees initial, 36 total, all in by 2800-3000 rpm
Third, I'd put headers and good duals with a crossover pipe, X or H, and I wouldnt be shy about exhaust pipe size, 2.5 inch to 3 inch, whatever fits in nicely, most shops will prefer to work with 2.5. If your current duals are 2.25 or smaller, they'll do fine for now, but realize that a 460 is a pretty deep breather and they like exhaust pipe diameter.
Finally, a shift kit, probably Transgo.
Those changes alone should get you better mileage and significantly more hot rod feel as well as torque in the mountains. Matter of fact, I bet it'd outrun 1/2 of the "hot rods" you encounter
When you are referring to the "swing" bearing, do you mean the two piece driveshaft and the carrier bearing that supports it? If so, don't sweat it, it's strong, the only concern I would have is with very high driveshaft RPM due to balancing and all those pieces working (or not working) together. But from a torque perspective, its plenty strong. Every tractor trailer on the road uses that design.
70 Sportsroof, 427 FE/489 cid, TKO-600, 31 spline 4.10, A/C. modified Mass-flo EFI/reprogrammed A9L/CnC ported Victor.