just to share my experiances with this conversion (well worth it)i have a 56 f100 by the way
1   -  the mounting bolts on the truck were 9/16"   holes on the bell were 1/2" these were drilled out
2   -the dust cover that fits to the bottom of the bell has a small threaded nut welded to it  the corresponding hole in the bell is also threaded   and needs to be clearanced. this is because of the proximity of the oil pump.
3   - this one is down to me i think,  i used a TCI converter and tig welded the studs as per instructions. they must have moved  as i had problems mating up to flex plate.    sort this out on the bench it's a swine to figure out on your back under the truck
i used an FE starter and have had no problems
there's a good article on this conversion on this website by Jeff Hallam
stuey