Why not use a V8 bellhousing with side mounts that will use the original crossmember? That way you can still use the original pedal and linkage from the 6 cyl. I dropped a 283 in my truck and used the 3815891 bell with the 3 speed trans and same clutch linkage that was on the 6 cyl. I'm still using the original pedals and it works fine.
The diameter of the front bearing retainer plate of your 4 speed will determine what bellhousing you use. A P/N 3815891 bell will work with the size retainer plate on the 3 speed. If the 4 speed plate is larger than the 3 speed's, you'll need a bell with a larger opening, such as a P/N 3925505.
You can use a V8 front mount setup. There are aftermarket ones available for just over $100.00.
If you don't go with either of these, then you'll need new crossmembers for the 4 speed and engine side mounts.
Here is a tech tip on bellhousings:
http://www.stovebolt.com/techtips/engines/bellhousings.html
