I've been having the same problem for the last two week logging on to this web site. I have a whole page in a binder of all the passwords that didn't work and then I'd get one to work and next time it wouldn't. It's working now.
Any way the average 390 was made to do 335 HP they did have a 401 HP in 61 I'd bet you don't have one. The oiling system is a problem with high revs, it will never be a 427 side oiler. You can make it better but never get to the side oiler level You can over bore 0.075" and call it a 406. but the quality of crank and rods will determine how far to push it. Remember this is a crutch engine. Build it right and you may have something to sell of value when you're done What are you doing for cam and lifters? There are a ton of point you can alter and there are some I'd intrust to a machinist. Above all I d go with a Melling high volume
oil pump. get the truck pump and the step down hex drive and do not add the optional shim the truck pump is 5/16" hex the car pump is 1/4" hex. The input in the pump tends to ware the most. As a heavy equip mechanic I spent a bunch over the years getting by with what I could afford trying to make it better.