it would be better to do that then use old parts for sure. i'm gonna recommend a three angle valve job again, 2 days of work and less than $100 and then you've got nothing to worry about. they can also check for warpage and cracks on the heads. i don't think it's as taboo as what people say, and i definitely know of worse. like my buddy that built a 3400... he reused all the bottom end TTY bolts. i about smacked him when he told me that