Need help choosing a junkyard engine

the 67 crank will elimnate fitment issues with your tranny. if you use the 74 with the 74 trans you wont be able to use your pushbutton setup. :

You can use the 74 engine with the pushbutton trans, by making or buying an "adapter" bushing to go in the end of the crank, and use the 74 flexplate with the 1963 converter.
http://cgi.ebay.com/ebaymotors/Torq...r_Truck_Parts_Accessories&hash=item3363e5a65b