Re: Need info for 302/351 build
91GT347 has made the assumption you have a Windsor, not a Cleveland. Since you have posted in the Cleveland forum i guess you know you have a Cleveland, not a Windsor.
If you are unsure, look at the front of the motor and if the timing cover housing is cast on to the block upi have a Cleveland. If you are still unsure post a pic and we'll tell you.
As for engines, the 302C and 351C have the [B]same[B] block. A change of crank,rods and pistons will increase your engine size to 351.
Depending on your budget, you could find these parts cheaply at the motor wreckers, or if you have a bit more cash, you could go for a stroker and get anything up to 408 cubes out of your Cleveland block. There are plenty of stroker kits around these days at good prices.
Given you have a heavy truck, a stroker may be worth thinking about. There are lots of guys on here that have done strokers and can help you get it right for your truck.
Hope this helps