just to let you know there are 2 types of bell housings for your clevo one fits a toploader the other will fit a single rail.
i'd recommend sourcing your own bellhousing, Dellow or something will probably have one that allows you to bolt up both boxes.
the toploader will handle most 351 combinations you can put in front of it and you can expect to pay alot of money for a toploader.
if your hell bent on driving a manual and don't have cash for a toploader you can probably find a single rail for about 50bucks, for a complete setup for a clevo i wouldn't pay more than $200 on a single rail, and it would have to have everything clutch flywheel pedal box... everything.
put it this way, i'm selling my mate a 351 clevo and toploader for $1500,