i have created quit the "crossbread" car. i have a 74 plymouth duster with a78 engine 76 tranny 80 something belhousing and an original hurst shifter from a early 70's a body.
and since it's a crossbreed as you stated, that may be the problem.
Everytime you make a minor tweak to the linkage to correct something, other things may be out of wack. Is your clutch freeplay adjusted properly? Is the clutch assembly new or is it a crossbreed as well?