The mileage would concern me.
Adding power to a bottom end without freshening up the lowers is asking for trouble.
The mod sequence I would recommend is a new oil pump, copper oil pump gasket, ARP oil pump bolts, replace the plastic oil pump connector rod end with a solid ARP steel pump to distro rod, fresh crank bearings and ARP Crank Bolts, not stretch to torque bolts like GM uses. Size and check the rods, lil' dingle berry, New Rings. Polish/file the oil pump gears before install.
New Seals... fresh bottom, then fresh top.
Know that is not what you asked...
The Jasper Marine I bought, came with brass freeze plugs and a Fuel Pump machined and tapped boss, in case I wanted to run a carb down the road. The GM casting was brand new from Mehico, machined at Jasper by the good old boys from Indiana. It also came with forged flat top pistons, Chevrolet Performance Crankshaft.
I cannot recommend Jasper enough, the way the engine turned out after what I thought was a nightmare.
Contact Jasper for stock heads or call a circle track engine builder/machine shop and buy good quality Vortec's or copies made from good quality castings. If you can possibly save your block as a backup build and afford the package Jasper sells, you'll be very glad you did, from my experience.
The racetrack head builders you'll find online from Indiana, Wisconsin and a few other states, have the secret sauce, however you'll only want the sauce on a good to very good bottom end, or you'll be back in there way too early and wast your money.
LTL shipping rates are about to freak out, so think it through quick before it becomes un-obtanium or outrageous to ship a block.
I have 2 sets of swirl port heads but you do not want them, really. If you were local... They are not worth the $85 each to ship them, is the problem. By the time you flux them and deck them and grind a 3 angle on them, all you have is swirl ports.
I guess you could try to find somebody here on the forum who is closer with similar low dollar heads, they don't want?
Good luck!