If a 390 is cheaper than a 348, than the 390 is already worth it.
It’s not cheaper for 390.
Going through Cambell industries, price is $1400 + $350 to balance = $1750. Shipping to me is $115, so roughly $2K
Going for 348 ci,
Crank $350
Pistons $242
Balance $250
Main bearings $50
Rod bearings $50
Rod bolts $56
Main bolts $40
Piston rings $75
Rod resize $150
Press piston pins $40
Total $1,217, with many items free shipping, and some combo packs, I am roughly $1350.
And again, 390 is choking through 1.88” standard 360 valves.
Does not make a lot of sense to be ready for up to 500hp, when I have no intention of ever exceeding 370hp.
Matching components to requirements is where I am saving money.
And I like it to spin a little quicker too.