well I know first hand that the MAC 1-5/8" longtubes work. Because I have them on my P heads on my car.
I put a heat shield boot on my #4 sparkplug because it was a little close, and put a 90degree spark plug boot end on the #7 because you cant fit the 135degree ones in that one. The other six plugs are fine.
A few of them are a little tight to get out, but I've gotten all 8 out while the engine is hot without burning my hands, so its not THAT bad.
On the tight ones, I just put the sparkplug socket on the plug, then I use a 3/4" wrench on the hex end of the socket to get it out instead of a ratchet.
Let me know if you have any more questions, and don't let the P head sparkplug clearance rumors scare you into buying those overpriced shorty headers!
longtubes for life baby
