Turn a small drill press into a Bore/ Hone. Bolt it to the top of your engine block & do your own machining .

Depending on the Piston type it will have the minimum X amount of clearance built into it. You can hone the cyl to however much you want. Have you mic'd the piston? Measure the piston. Leave yourself room for finish honing the clearance in. Couple thou worth. What ever the manufacture recommends..I add .001-.0015 to it.
Forged Aluminum dished for the 4" 390 combo