Canton remote canister and their tall (4" something) cartridge. 3qt Accusump, Canton's
oil thermostat and a Setrab 915 series
oil cooler. Plumbed with AN-12 lines.
Are the spin on mating surfaces smooth & clean? The O-ring gaskets lubed before filter installation? Is the leak coming from somewhere other than the filter/mount area, perhaps an AN fitting?
Heat and pressure, what? What makes
oil in a Roush 427 different than other small block Fords? Do you have more oil pressure, 50-60 is about normal? Heat, are you running road courses and spinning 4-7,000 all of the time?
I find that the water gets hot when sitting in traffic or at slow speeds, once at speed the water runs under 100C, never a problem. Oil is good at slow travel and engine speeds and doesn't become a heat problem until running hard on a road track, never an issue on the street even with the stock Mocal oil cooler.
Not sure if dual filters are necessary but it's your pleasure. They will offer additional flow restriction which may cause the oil pump to work harder. Life is full of trade-offs.
I'd look for another mechanic and other causes of the problems. There are a bunch of good spin on filters but I haven't run that style in many years.
Jim