Dave just barely snug about three bolts with head gasket no big deal--with Harlands you will notice that the old two thread rule may have the adjusters a little deep--I would say one thread showing--The SECRET is do not try and figure the BS effective length--Just do a very simple overall length--the diff in cup depth between makes is negligible Smith Bros and an overall length is the key
You can screw up maybe .025 and still be aok but use a height gauge or a big caliper not a tape measure and just round it off don't order some crazy 9.316 stuff OK?
Also check first many Harland applications need lash caps to help ( not correct) geometry A Sharpie is your friend here--Sharpie up the tip or lash cap and then just slide the rocker across the tip several times-- adjust pushrod length to keep it as near center as possible - this is done with valve closed at rest never mind cycling it as your adjustable pushrod will just collapse under the spring pressure-while this is not perfect to make an A on a test it is for sure good enough to run the S%#@ out of any Mopar Now it is best to jimmy up some kind of pushrod near the correct length and check geometry but if it is whacked what ya gonna do--shims? lash caps? Let us know if you need more help