Dingocooke Steve There have been a ton of guys on here with buildup over the years. The 2 things I will tell you from 15+ years of abuse is save your money and buy a Barry R. stroker kit. The 4.25 kit is solid and come balanced for a couple of extra dollars. Revving the crap out of a 427 oem bottom end is a shoprt life if you like racing and road course driving. The last motor to blow on here was Sammy's. This was a well built motor that on the street would last forever. ON the track it broke. Read the story.
Oil pressure with an FE bottom end is min of #80 psi and if racing running a #100 pound spring is safe with a large 7-9 quart pan and a 2-3 quart accusump. With a BBC rod bottom end, so far 80# seams to be working out OK. The rods weight less and the bearings are wider. 60# is for street car only IMO. I have run both ways. .080" jets in the heads for limiters.
You need torque to move your car, not HP. HP is for doing 140 mph and holding speed. Finding a good machinist that knows FE motor is another issue. The other limiting factor is you are running a small camshaft, any thing past the max HP output is just wasting motor. If you can turn 6,000 rpm and save the motor, why go to 6,500 rpm for a shorter life. Your money, time, and motor. My 2 cents good luck with the build. Ps it's hard to get parts in GB, break that motor and see again how hard to get parts. What's the matter with not running a Cleveland?? 600HP is easy with this motor and again oiling modes. Plus you can turn 7,000 rpms easy. Rick L.