use loctite 567 or that permatex stuff
http://img-asia.electrocomponents.com/images/R330394-91.jpg
http://www.henkelna.com/cps/rde/xchg/henkel_us/hs.xsl/product-search-1554.htm?iname=Loctite%C2%AE+567%E2%84%A2+PST%C2%AE+Thread+Sealant&countryCode=us&BU=industrial&parentredDotUID=productfinder&redDotUID=0000000JBE
put some on the threads, and wind them in with your fingers, dont torque them to anything, just so long as all the threads are in, then put the head on and torque the headnuts. OEM torque for the headnuts is like 22ft/lb's, not sure if its the same for the t-rex set-ups.