The stock radiator should give plenty of clearance. Is it posible the mount was modified for the other radiator?

I'm not aware of a "short" pump for a GMC engine.

Lot's of guys on the discussion board at www.oldgmctrucks.com run 302s. You'll have to sign up and do a search.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.