Glad to see the 413hp cam was clarified, IIRC that cam is the same as the long-ram cars of years earlier but with different installed CL, the crossram cars require very specific valve timing. I believe they installed the cam differently in the L, but I've never researched that, and I'm willing to be shown to be wrong. Also, IIRC only the shortram cars got the solid-lifter cam.
As for cams, might as well consider a more modern grind, no need to stay with something from 50 years ago. Yes, the factory stuff was decent, but there are more options now. I would recommend the Lunati Voodoo 60302 (although it's a different part# number now) but you can get a whole bunch of other opinions on that can of worms of camshafts.
Don't rebuild an engine just for the sake of doing it. If an engine is running well and has 10 psi of oil pressure (hot) per 1000rpm it's not going to 'scatter'. Keep in mind that's an old mechanics rule, and is based on crankshaft psi like the Brand-X engines -- our OP is measured above the camshaft, after a few more pressure drops have occurred, so our crank pressure is higher than our gauge shows. If you have 50psi (hot) at above idle you'll be fine for a cruiser.
If you have some blowby in the rings, that may get worse with better-sealing heads, so you might find yourself digging back in to do a dingle-ball hone-and-ring job. But I believe you will have a hard time finding pistons and/or rings for a 413, they are an odd bore size that doesn't cross to other car manufacturers. If you do find pistons, they'll likely be low-compression versions. If you get custom-made pistons for better CR, well, at the end of the day you've spent a lot of money and still have a 413, where the only benefit is you can tell other people you have a 413, which sounds mysterious, some of them might think you have a Beach Boys Max Wedge. Better to consider other engine options at that point? Although in a 65 C-body you have that driverside engine mount to deal with, and not all blocks fit nicely with it. Don't get me wrong - I liked the 413 that was in my 300L, it was torquey and had great throttle response, far better than the 452-headed 400 that replaced it, but I would never drop big money into a 413 if my goal was to get my money's worth (and it usually is).