i wouldn't worry about spending all that loot on the AFR heads. they are nice pieces, but the price tag doesn't really jsutify the gains.
TPI relies on a strong exhaust side on the cam to make top end power. look into a comp cams extremem energy roller. something along the lines of a XR276HR or XR282HR to get things moving better, look at the XR288HR if you really wanna put up big numbers.
for heads i woudl say keep it simple. torquer305's with a mild p'np/gasket match to the intake or some L98 vette heads and base manifold matched would get the 300hp job done easily for half the price of the AFR's.
porting out the intake, high flow runners, and a ported upper box are a must. get everything gasket matched up and hogged out as much as possible. there may be a need for a little larger TB, and of course tunign will be key to your success.
300rwhp is not a big deal. i woudl say aim more for 350ish to make it fun
