I just did my manifold gaskets. IIRC they were 9/16" but there are 2 different threads on it. Just reuse the old stud and bolt, thats what I did with no problems.
84 CJ-7 Renegade- 258,GM TBI w/ ESC, HEI, T-5, D300, D30, AMC 20 w/ trac loc and superior shafts, 2.5" BDS lift, 1" daystar BL, MORE shackles, Tie rod flip, 33" Swamper SSR's, Full cage, OBA, A to Z rocker guards, A to Z rear cage, Warn 9.5ti, Taurus fan, Herc'd tub, LED tail lights, Hand throttle, Hella Fogs, Hella headlight conversion, more to come...
02 WJ Limited, 4.7 H.O., RB1 Nav, DD and toddler hauler
Checkout my Junkyard TBI writeup: http://www.bustedjeep.com/projects/junkyardtbi.asp