hello. i have been speaking with many mechanics, and im getting mixed answers. i was wondering if anyone can give me some solid information. i have a rebuilt gm 5.7 longblock that i purchased to replace with my gm 5.7 engine. both of these blocks have the same # gm 3970010 labled on them. the problem is, the old engine that im swaping all parts over from to new block has a 8 inch harmonic balancer. but the new longblock came with a timing tab for 6 3/4 balancer. is it ok to swap the tab out with my 8 inch timing tab, so all my parts will go on? or do i need to use a 6 3/4 balancer? and the other question is, if i change balancer, do i need to change flywheel? because i also have another parts motor, 1985 mercruiser 5.7 engine with 6 3/4 balancer with smaller flywheel, and the gm engine with 8 inch balancer has a larger flywheel. i know im asking many questions, but, what i want to know is does it matter? can the flywheels and balancers be mixed around? will my rebuilt longblock accept either size balancer without doing damage? some people are telling me it dont matter. some say it does. any info would be much appreciated. again, both my old gm motor and the new gm longblock have the same numbers on them. thanks my boat is a 1985 formula 25pc with mercruiser (GM) 5.7. alpha one