Question on trans tunnel clearance...

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Island67DartGT

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I have a mildly built 400 CI big block with a 727 TF Trans I'm planning to install in a 1967 Dart GT. The car is originally a /6 (with /6 K member - and I "DO" have a Schumacher kit). I've measured the length of both trans (previous)904 - /6 and (future) R/RB 727 and both seem to be close to same length from center of crossmember mount to mating surface with engine.
Question I have is, will I need to do some mods to the body joint line where firewall mates to floor pan in order to set 400/ 727 in place once I use the shims provided with the Schumacher kit to gain clearance for headers and oil pump (after I notch the drivers side K Member mount)?
Someone said I might have to do a little cutting and hammering at that seam for clearance.
Also... will the original /6-904-7 1/4 rear driveshaft diameter be sufficient? I know I will have to change both yokes to accommodate the 727 spline and the 8 3/4 "741" 3rd member I have. I have to find out what yoke I have on the 741 still.
 
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You will definitely need a shorter driveshaft. The 727 is 2/2.5 inches longer. Not 100% sure but I think the Axle Center line to pinion yoke is longer on 8 3/4.
 
You will definitely need a shorter driveshaft. The 727 is 2/2.5 inches longer. Not 100% sure but I think the Axle Center line to pinion yoke is longer on 8 3/4.
Thanks George.... But I'm asking if the original driveshaft I have (which is originally a Slant 6/ 904 Auto and 7 1/4 rear is strong enough. Diameter wise). Or should I find a more beefier shaft to have fitted for what I'm planning to do. I don't want to waste money on trying to resize my original driveshaft if it won't handle a big block. I do plan to rebuild the engine for more power eventually.
 
I have the same kit in a 74 se, no problems with the tunnel clearance and you definitely want a 8 1/4 or larger rear. I have a 8.25 track loc with 3.55 gears and it stands up great. I think my driveshaft is 44.5 long. Had a new one made for 220 shipped.
 
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