bridged heads
IIRC it is .250 and then another .125 for the guide plates
so final milling would be .375 to retain stock geometry with 1.6:1 harland sharp roller rockers using arp 7/16 base 3/8 studs.
i shouldnt need longer pushrods (stock being 7.800") unless i go deeper or use crane roller rockers. i seem to recall years ago doing one with guide plates and going too deep or the combo of that and crane rockers and the result was needing .100 longer pushrods @ 7.900" to keep geometry correct. i may still end up needing the longer pushrods but i'll check that when i put her together
drill and tap studs to 7/16
Any feed back or corrections on that info machine shop going to work on this in the next day or three.