im triying to do B20 block whith a P75 head from a B18A, wich head gasket you guys recomend???, the one of the B18, or the one that comes with the B20????

Take your pick. I would go witht he B20 myself, only because the Honda dealer is closer than the Acura dealer.

go to the 4th gen part and look for a guy named bambam he knows every thing about a b20

You want the head gasket for the B20. The head gasket for the B18 will have a 81mm hole for the cylinders and the B20 gasket will have a 84mm hole for the cylinders.
Also which B20 block do yo have? B20B or B20Z?