I'm running a 588 cube Hemi on alky, 4.50 bore 4 5/8 stroke. I have been told it would more power if I down size to a 526, 4.50 bore 4 1/8 stroke. It was explained the extra boost would be made and RPM would go higher, this would crank it up. Is this something I should consider doing?

Theoretically yes. More RPM, more HP. You may be limiting your HP by your rpm limits of that big stroke 588. But you should be able to make up for it with your boost and lower rpm if your current suspension and tire combo can handle it . What is your RPM band right now?

I've been keeping the limit at 7200, Launch at 3200

What it looks like: RPM increase matches stroke length decrease.
4.625" / 4.125" = +12.1%
But it doesn't - RPM limit is inertial load on the rods, which only goes up inverse to the square root of the stroke change.
The product of shorter stroke X higher rpm at the same stress level is lower than the original.
1.12^.5 = +5.9%
The blower's pumping loss also goes up quickly.
Remember: boost pressure is bad, it's resistance to intake flow.

Could it work?
Sure, it's your (a lot of) money.

It just depends how big the blower is. If it's big enough to feed a big motor, then it'll make more power with the motor big. If the blower is too small, you could keep it in a better efficiency range by making the motor smaller.

What is the overdrive now?
And how much boost at 7200?
Just curious where it is at now.

50% over, 31lbs, I'm really not sure if my old blower really has that much more to give

This is a matter of piston speed with that large of crank. Too much makes the motor less efficient and limits RPM which is important with a blower. There does seem to be a sweet spot and I believe it's about 526 cubes with a 4.15 crank. My present motor has a 3.75 crank and 470 cubes and it makes a whole lot of power with twin 98's.

Our new motor has the 4.15 crank and 521 cubes. Not so much for power but for quicker spooling.

When you get into the 50% use things are not as happy as they can be unless the blower is top of the line and I am not sure what that is now days.

Chris Cadetto went from a 588" down to a 526" and he said he makes a lot more power and his et times show it.

Yes he did, but his has really evolved through the years into a Monster, way more than cubes changed and I love his 1871

I have heard the sweet spot is 526-540 range, I didn't know if anyone down sized to make more power and how it worked, mine worked great as a torque monster on the street

One thing to keep in mind when compressing air, it takes power to compress it. The higher the pressure with the same size compressor the more power it takes to make that pressure. A bigger compressor turned at a slower speed that makes the same pressure as the smaller compressor will probably go faster in a race car with good traction
Another thing to remember is compressing air makes heat, hot air expands and take up more space than cooler air does
I can't remember the HP lost due to changing the manifold inlet temps from. 130F to 190F by letting the motor warm up more before making the two pulls with no other changes, it was more than I thought it would be

Sounds like it might help but not enough to bother right now. This guy is selling a sweet billet 4 1/8 crank, I'll probably buy it and throw it into inventory and save it for the next major rebuild