I recall using 3/8" grade 8 bolts for my 250. The length depends on the engine stand, mine has 2" standoffs. The flanges on the engine are about 3/4" thick, so figure something in the 3" to 4" length. They're cheap, buy a bunch of different lengths.

-Boyo

'48 Willys CJ-2A / '55.1 Chevy 3600 / '66 Austin-Healey 3000 / '04 Volvo wagon (parenthood!?)