I have personal experience with Chandler. Their product worked for me. I bought the one with a lifetime warranty. It fit great and when i fired it up after getting all the other pieces back on, it was like a new car!!
I've had my 93 Vette for 18 months, and my old Opti must have been going bad for a while, 'cause now it runs better than the day I got it!!
Whatever you do, don't forget to spring for a new water pump. Mine was working fine, but I sweated and cursed so much during the install, that I didn't want to do it again in a year or two due to a bad water pump.
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Rarely indicted, never convicted