[jhv48]

I had an FFR with a 302 much like yours. BUT, I had 3.73 rear gears. Made my engine come alive. If you don’t want a power adder such as a turbo or supercharger, lower gears are your least expensive option.
Luckily, you’ve got FI so you don’t have to make jet adjustments for high or low altitudes.
If you do decide to swap out the engine, and keep the 3.31 rear gears, look for a torquer engine, not a revver. Lots of torque right off idle. The reason is that your rear end will work against you at that altitude and you’ll never get to use that overdrive 5th if you have a high strung engine.
I currently have a 560 lb/ft engine and a 3.46 rear end. Would love a 3.31 as it would make first gear much more useable.