I dont mean to be rude, but this question has been asked 1201029014319089246y8944-1283-81953280028945720/G times.

Ive answered it if you would read the STICKY at the top of the forum or if you did a quick search all questions would be answered.

But since im bored.

The GSR head adds .3 compression because of the quench pads on the combustion chamber.

As far as FLOW, they both almost flow the same, and the difference is so minute you couldnt tell the difference at all. There is no HP difference.

Both heads will flow an support up to around 200whp before they need to be ported or worked.

Most people go with the GSR head because it gives them .3 compression without having to do anything to the pistons or valves or worry about valve to piston contact.

And a Poor Mans ITR would be

GSR block, B16 head

A GSR block with a GSR head, well, that would be a GSR LOL

Personally id run a GSR block, PR3 b16 pistons, GSR head.