The boost pump is specific for Fuel Injection but attainable easily otherwise. It's not a deal breaker, just trying to save you a few $$$.
The IO-320 with the Bendix Servo will accept non-ethanol MoGas* and it's a Wide Deck engine which means higher Compression pistons are possible as you mentioned. After my original RV4's ND 0-320 reached TBO, I retrofitted a 0-320E2D (WD), rebuilt and balanced with 10.0:1 Comp forged air-boat racing rods and pistons in my own RV4 later and it was a worthy mod, significant improvement. No added weight and 170HP. With higher Comp I mixed my MoGas 25%/75% with 100LL based on a Canadian study I read.
Light+simple=Max bang for buck!
Good luck with your decision, my 2 cents notwithstanding
*Check this out:http://www.utias.utoronto.ca/wp-cont...aded_fuels.pdf