The 95TM-98TM heads were a lot better than the 91TM, and even the 93TM, but still, the factory ones seemed too weak and cracked.
Just seems like you might have been better off starting with new aftermarket ones at ~$200 a pop, then they'd already be improved and you could just have port matching done and that's it, saving money on the labor and having stronger better flowing heads.
A little late and not too much help now I guess.
Should be okay up to 10:1...maybe. Might need premium gas, might need a tune. Don't let 'em go higher or you'll need stronger head bolts to keep those things from going through the hood..or blowing gaskets.