Stroker Motor Question

Up to about 650 hp both will work fine. The 400 block is a bit stronger in places and if I was going over 650 hp I would use the 400 block if I was gong to stay with the stock block but much more hp and your getting into aftermarket block territory. Myself my 493 is a 440 block as I wanted to have the selection of the 440 intakes. As for reving once you stroke it then it will depend on the stroke you use as to how quick it revs. In stock foorm the 400 revs faster then the 440 do to its short stroke but when stroked it may not if you put a long enough stroke in it. Ron

A good, sonic tested to make sure the cylinder walls are good, 400 block has a lot thicker main webs than any stock 440 block, Mopar made them that way for a reason The 440 blocks have weak main webs and will crack once you get above 600 and detonate the motor even a very small amount, been there done that Add a set of after market steel or aluminum main caps and go crazy, I have My last pump gas 400 stroker motor, 518 C.I.,made 727 HP on Oregon pump swill, it had a bunch of good parts in it also You can do the same thing, use a 4.250 or 4.300 stroke crank made for a low deck with BB Chevy rod journal sizes and a decent set of long forged steel H beam BB Chevy type rods, (6.700 works very well ) rods and shoot for under 11.0 to 1 on the compression ratio with aluminum heads, I shoot for 9.5 to 1 or under on all my pump gas iron headed motors. Lots of choices out there, make the correct ones and have fun

I built a 4.15" stroke 400 block (499") to take 700+ HP and 7,000 RPM, but it also has the BCR aluminum main caps and girdle, 1/2" internal oil pickup, and Edelbrock victor max wedge port size heads.
As mentioned, not much selection for intakes for the combination, Just using an Indy Single plane right now. The 400 does fit the engine compartment better, not just hood clearance, but clearance to the passenger side inner fender is better (headers and spark plug clearance.)

I also have a mild street 440, 0.030" over with the 4.25" stroker crank and 7.1" rods. It has a mild hydraulic roller cam 10.3:1 compression, and fuel injection. It might be making 550 HP, but a ton of torque. I have the rev limiter set at 6,000 because of the hydraulic cam and lighter valve spring pressures. This engine has mildly ported 440 source stealth heads. When I built the engine I was going with a more stock look.
If your building a 500+" stroker engine for power, you will want to use a larger Max Wedge port cylinder head. If you plan to make over 750+ HP, use an aftermarket race block. By the time you modify a stock block with oiling mods, and main caps and girdle You could almost pay for the race block.

For your application, I'd go with the RB motor.