Cyl. Heads question
the best flowing LS1 heads have the 241 casting numbers. and i think that you can bolt them right up to a 98 if you have the correct valve covers.
porting and polishing is a good idea if you have someone who knows what they are doing port them. 5.3 heads should be ported before installing them to make it worth the work of installing them, and to get good hp numbers out of them. you need to have a cam and heads combo that work well together to maximize you hp.
Do you know what a rough estimate would be to port and polish the heads? On my LT1 heads local places wanted around $700 to port and polish with the valvejob. If its that much I might as well just buy some Patriot heads or something. both Livernois and Patriot have CNC'd LS6 heads for less than $1000, and they will flow better than PnP LS1 heads.
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If you're really budget constrained you can also look into milling your 5.7 heads and running a thinner head gasket to raise compression. Although most thinner non OEM gaskets are 2x to 4x the price of OEM gaskets, but still cheaper than a set of heads.
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If you're really budget constrained you can also look into milling your 5.7 heads and running a thinner head gasket to raise compression. Although most thinner non OEM gaskets are 2x to 4x the price of OEM gaskets, but still cheaper than a set of heads.

