There's nothing wrong with P heads. I've got some and love them. I'm running a stock cam with 1.7 Cobra rockers. From what I understand, I can't put even an E cam in without switching back to 1.6 rockers. But I got mine for 225 bucks and they had 67,000 miles on them. I put them on straight, didn't even change the valve springs. My old MAC headers worked OK with them, I just put a shorty plug in cylinder 7 and plug wires for an 89 Blazer on it.
At the same time I put an Explorer lower intake with a Downs Ford upper, Explorer 65mm TB, 65mm EGR, and 24lb. injectors. I like the combo, it pulls hard up top. My only regret is not changing valve springs.
Oh, and my block has 182,000 miles.......that's HARD miles. It runs great.