[RustyPile]

IMHO, that's not a good reason to replace the starter with either a "modern design" or exact replacement.. Those loose terminals and posts can be easily tightened.. So easy you may be able to tighten them with the starter in place.. You can tighten those posts or you can lay on your back grinding away at the bellhousing trying to make a different starter bolt up.. But it's your truck and your money, you call the shots....

In reference to the "hodge podge" of parts that make up your engine.. Throughout the SBC's lifetime (1955 to around 1999), parts have been interchangeable -- heads, intake and exhaust manifolds, valves and springs, blocks, water pumps, fuel pumps, etc... That's the good part about owning and working on an SBC -- parts are available EVERYWHERE..

If you're really concerned about the actual "genealogy" of the block, on the bellhousing flange at the back of the block is where all this information is located.. The date code indicating the year the block was cast is a raised circle much like a sundial. An arrow in the center points to the year. If the engine is in the truck, you'll have a difficult task seeing these numbers. Distributor, valve covers, brake booster, throttle linkage, and firewall are just some of the obstacles blocking your view.

[EDIT]

Upon closer examination of your starter picture.. Referencing the battery cable post. The nut that holds the post is missing. Look at how the other large post hardware is arranged.. Replace that nut, install a lock washer, next is the battery cable, and last to go on is another nut. With the lock washer installed under the cable, the cable won't try to rotate on the post as you tighten the top nut.