Brent, if you bore the cam tunnel in a topoiler style block, you should look at making the oil groove deeper. I usually make them 427 size and depth when we bore the tunnel because you have to fix the groove anyway. Some 390 blocks have a very shallow groove even before boring the tunnel. There are 60mm babbit bearings for the 2.500 bore.
I turned one of those "dueling 390" hydraulic rollers 7500 on hydraulic rollers just to see if it would go there. Peak power was at 7000, but it did not float at 7500. Ford non-adjustable, conical spring, 11/32 valves. 240/248 at .050........it is doable.