""Any more input on these heads""
Not the stock Promaxx but I do on Todds Sidewinders. I bent a valve on my 2.02" bowl blended J's this past Spring and that is when I bought Todds bowl ported Sidewinders for my stock stroke 340 (+.040"). With no other changes, new heads/gaskets came out to the same 9.7 compression as my J's. I was expecting the bottom end to be a little soggy since these heads were tested at 280@.550". At 30mph, I can hit WOT and spin my new Nitto 275's. I tried this several times on several different occasions and each time I was breaking traction. It pulls harder on the top end at WOT too. I purposely did not change the cam (mostly because I did not have the cash) because I wanted to feel the difference with just a good head swap. Now after running these on the street for the late Summer and early Fall, I now want to make a cam swap this Winter. I think there is some more in it than my current 226/238@.050", .538"/.528" hydraulic FT combo feels.
My Yella Terra 1.65's bolted right up and my 5/16" push rods had no clearance issues with the existing HFT lifters. My Powermaster alternator mounted up just like before, and my stock valve covers fit too. I did have to go to a one step hotter spark plug after a few test drives. But this was an easy head swap for the average wrencher like myself. 👍