Motor is a 1990 TBI 350 with 198,000 miles. Started missing 2 days ago tuned up with plugs, wires, cap and rotor, and then yesturday, it started clattering like a diesel. Pulled the valve covers and everything looks good. Checked compression and all were around 150psi except the 2 center cylinders on the Pass side, (4 and 6 I guess?) they had 80psi each. I'm thinking blown head gasket between the cylinders. Hopefully replacing it would fix the problem, but then I'm at a crossroads. Should I spend the money to fix it, and cross my fingers that It lasts considering the mileage, or should I swap out for a crate motor. This all has to happen fast as this is my DD and the only in stock GM Crate I can find is $1964.