Most likely best off modding the 715 shafts if you have to as they will have the correct ends for the case. Might be cheaper to bolt in the Chevy stuff and fab mounts instead of buying adapters, but that is up to you. Not sure on 465 length vs. T98 Leave the Tcase there and set the engine wherever it needs to go to keep the shafts untouched. My truck that has the Chevy adapted to T98, the engine sits really tight to the firewall to the point where HEI ignition won't even fit. If it went forward 4" it would still have plenty of room....