With the longer rod you might want to check valve to piston clearance. You said it was a hemi, didn't you. Do you already have the 275 cam? I'm sure you know that's when to.check ( with cam installed ). You'll be + .045" lift over stock with that cam, and another + .020 with the longer rod. Not all that much, but the duration of the cam could come into play. Also ( my experience anyway ) very limited supply of head gaskets available. Only thing I could find was stock, and had to order a complete engine set. None of the kart supply shops I checked carried any gaskets for the 301. This was almost 2 years ago. Maybe that has changed. You can find head gaskets for the 212's in at least 5 different thicknesses and 3 different materials. I think the 301 is the ugly step child. Everyone wants a 420.
I haven't ordered anything major like that yet at all.
The 301 is the smallest big block and apparently has the nickname "the middle block" despite clearly being a big block bottom end.
As stated by Pancho, the internals are very 212by design, just beefier. I'm sure you can imaging my surprise to find the governor on the crank cover instead of the usual location.
UNLIKE a Ducar212 or a Predator Hemi 212, this has a dished piston like a wedge head always has stock... +020 will bring the crown edge flush to the deck leaving the center 80-85% of the piston 050 below deck level.
I'm definitely not one of those dumb@sses that slaps everything together and fires an engine up on the assumption I know everything.
It will be at the very least hand rolled over without a plug feeling for anything that feels like a problem then proceed with caution from there.
As for clearance checking, I prefer play-doh; it sticks less than that greasy modeling clay crap... even a pad wet folded paper towel is better IMHO.