The three speed won't work but they 302 will bolt right in once you find the correct frame and engine mounts. Since the 68 came with a 6cyl it won't have the correct mounts for a v8. A C4 transmission should bolt right up to the orginal transmission crossmember once you get the 302 installed. Also, some or maybe all of those 6cyl mustangs came with a POS rear end. Most of the ones that had v8s had and 8" or 9" rear end.
A 302 will bolt right in...
They came with a 302 from the factory in '68.
You'll need to use an early oil pan though and '68 motor mounts as well. Is the 3 speed a C-4 automatic or a 3 speed manual?
Either way, I don't "recommend" using a 6 cyl tranny behind a V8. Also, 6 cyl cars came with a very, very weak rear end. Its recommended that they are swapped out. Oh ya, the 6 cyl suspension is weaker than a factory V8 suspension and has smaller brakes too. Definitely recommend upgrading that as well.
All in all, the classic Mustang hobby doesn't find its worth the labor and costs to properly convert a 6 cyl to a V8 car.
I've got a '66 coupe so I've got a lot of experience with the older stangs...
Not positive on the '68, but my wife's '67 convertible (6-banger) has weak 7.5 rear-end. Also, I had a '67 Fastback 289. The 289/302 C4 bell-housing is definitely bigger than the 6-cyl C4 housing. Also - I've pulled both C4s and I'm pretty sure the TC is smaller on the 6 - because the flywheel is smaller.
(I've been wanting to do the V8 swap for a while also...) Mark
Check out a yahoo email group called resto-mod mustangs. Also, www.windsor-fox.com is a specialist in converting the early stangs to late model drive trains. Mostly for the fuel injection stuff but they have many pieces for the transmission swap too. Good luck
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