Personally, if the truck is a serious keeper, I'd spend as much money as you need to get the right transmission. In daily driving, lack of another gear or too much RPM ruins the trip for me even more than not enough power.
Close ratios? Very rare to get these in a truck-specific box.
How to tell what you need?
It's mostly how wide your engine's "happy" RPM range is (definitely not peak power), and how fast it must turn to get off the mark.
A highly tuned 250 L6 and a box-stock and tired 350 V8 may have the same power, but the 250 will fall on its face with truck (wide) ratios, and the 350 will almost not care - a Cummins won't care at all.
More cam, bigger ports = closer.
