ARP main studs for a windage tray

I guess if I can't find the impossible to find factory bolts then studs are my only alternative?
Pretty much.
And I'll get flamed for saying this, but I wouldn't overly worry about line honing the mains with studs. Mic the saddle bores across a few different axis to confirm if it concerns you too much.
Just adhere to the recommended torque values for the studs (not the bolt torque)- fine threads exert greater pressure on the caps than coarse threads and can distort the bore if exceeded.