You must be a little fuzzy on the numbers, but it's clear what you mean. My hemi got the stock rod replaced with a billet rod that's .020" over stock length, which brings a flat top piston to .005" from top of cylinder without any machine work being done. Since the most important thing you can do to save your engine is replacing that stock rod, then it makes perfect sense to do it, and wouldn't make any sense not to get the billet rod longer for the same price as a stock length rod.
There are various thicknesses of head gaskets out there, but my performance guy up in N.C. puts a .012" stainless steel head gasket in his hemi high performance gasket set. Here it wouldn't make much sense to stay with a stock thickness (.050" ?) since you need to buy a sump sidecover gasket anyway because of the rod change, and if you get the whole hi-perf gasket set instead ( $14 ) it's only 4 bolts on the head to change that head gasket after the 4 bolts on the valve cover, which also gets a new gasket in the set, and not a cheap paper one at that.
With my piston and head brought .058" closer together with the overlength rod and thinner head gasket my compression's greatly increased and makes a lot more horsepower. This setup is what the best small engine performance expert I know recommends and sells for the 212 hemi, and nothing hits anything. At least not with my stock pushrods, valves, retainers, and lash caps. Speaking of which.........
My guy says the stock valve retainers are the weakest link in the valve train when running new 22# valve springs like on mine, and are only good and safe to about 7200 rpm.
Want to know how close the piston gets to the head? Unbeknownst to me, my sloppy welding on a temporary header for testing before the changes caused a piece of steel welding slag to fall down through the exhaust valve into the cylinder. It was a little round ball not even near as big as the size of a standard .177 BB you were shooting as a kid. It was discovered when trying to rotate the engine for access to the rod bolts, and the motor would have to have a little firm head start to twist it past top dead center, or it would hang up there when turning slowly, only go backwards. That was with the stock rod and head gasket.
BIG NOTE: Please follow the instructions that come with your billet rod to the letter. The new bearings get mated to the rod in that process, and it's all really necessary. Torqueing by 20's to 100 and back down, then by 20's to 170 and then taken apart, then by 20's to 170 in the engine. All that will be wrong if you don't first dip the rod bolts in oil, they're special "yield-to-fit" bolts. Remember, rod bolts to inch-lbs., NOT foot-lbs.
Best of luck to you.