Tesar Race Engine tubed the pushrod holes with thin stainless tubing. They bedded them with loctite sleeve retainer sealant. I realize the hole would have to be reamed, but it’s a pretty good solution.
I wish I could that something like that, but before I started my porting I had the machine shop do a clearance cut on the pushrode hole to give me room to run a 3/8" pushrod, which means that the hole is now actually oblong, no longer a nice circle. I figured that in order to put a sleeve like you suggest, the machine shop would have to re-cut that hole much bigger and it honestly doesn't look like there is that much room left in there.
