c6 valve body differences

have a 67 c6. Got it rebuilt, somewhere along the line the trans shop swap the vb for a 77 which has no detents in the manual valve. concerned i took it back, brought along a 66 vb i had layin around and they went through it. no 2-3 shift probably a green dot. anyways long story short I put in a manual vb that has no detents in the manual valve. the B & M shifter provides gear selection but i'm worried it'll slip or lose adjustment. Can I just swap out the 77 manual valve for the 66? There seems to be differneces there so I don't know if it wil work.