Was cleaning the engine compartment of my escalade ext and saw that a couple of the stock bolt heads broke off the passenger side exh manifold. I'm gonna take it to a local shop to replace all the bolts (both sides) w new better bolts. I liked the arp bolts but there are a bunch of part numbers that says would fit with different underhead length (uhl). Do I need 20mm, 25mm or 30mm? Thanks