At 6000 ft above sea level a 300HP motor only puts out 200HP or so on a warm day. I'd say a 225 LPH pump is not going to be taxed on volume and they are all designed to run at high pressure, but the heat does kill them off early. I've tried many different brands of inline pumps on many applications over the years and never seen one last a year.
I also hear the Wabro's are widely counterfeited, so you may be getting cheesy Chinese knock-off's. I run a spare pump from my C4 Corvette in my tank. I've never seen one of them fail yet. The C4's LT1 was port injected and also rated at 300HP at the crank. The C4/LT1 (92-95) pump is quite small in diameter, and comes on a stalk with the fuel sender. It might be quite easy to retrofit one to your tank.