Flathead water leak

Got my flathead runnning last week, and it runs great..Theres one water leak coming from the p***enger side water inlet. Ive taken it off twice, made sure the thermostat was seated properly, re-gasketed it, tried different gasket sealer, and it still leaks. im using alluminum water inlets on vintage fenton heads.

Any suggestions on how i might fix this leak...I feel like the surface of the head may be uneven, but am hesitant to take a flatfile to it.

thanks

 

First, hope for an easy solution...get iron stock water castings, replace bolts into head with studs, and see if that will clamp on new gaskets well enough...
When that fails...I am such an optimist...
Get a good big mill file, lay it across the opening, stuff the opening with greased rags to catch shavings, and file, letting the surface guide the file. Study the resulting shiny spots, or color that flange with a magic marker as a guide to high spots, and see what emerges. The file will tell you how irregular the surface is, and maybe allow you to correct it easily. Filing will be severely
restricted by fins and head nuts, but you can probably find an angle that will allow the file (or a piece of the file) to lay flat and be moved for at least a short stroke.