elderbrock performer 600-750,, or stock 625 afb ??

750 is too big for what your intentions are, Big is NOT always better unless there a set boobs, & even then theres a limit there 2, stay conservative sense its a 318 & primarily street driven.

Here is one of many on e-bay.

http://cgi.ebay.com/ebaymotors/Edel...r_Truck_Parts_Accessories&hash=item45fc5f1c10