without knowing all the info: how far the pistons are in the hole, head gasket thickness and the CC's on the heads any guess is at best *SSWAGITD
J heads are usually in the lower 70's range but are listed as having anywhere from 65~74cc chambers. so, let's go with the middle at say 71cc, with a .039 compressed gasket and the piston isn't a million miles downtown and you *should* be darn near 9.5:1
however, if those are positive deck then you're probably closer to 10.5 but if they're down in the hole a ways 8.5
*somewhat scientific wild *** guess in the dark