I am concidering replacing the rocker's on my engine this winter as part of a winter freshen and upgrade with either Harlan Sharps or T@D's,,my question is do they make or have beehive's that have around 250# on the seat ( i'm not sure of open pressure at this time) so that I can fit un modified/ un special made rockers as I have 1.550 dia springs and the rockers don't have enough built in clearance and have to be re cut/modified for this dia spring, or am I stuck using a std but smaller dia spring like a .470/.
500 if I can get what i need pressure wise.

I'm not positive on this...maybe a builder can comment, but i think the beehive needs less pressure due to it not having the same tendency to float from harmonics. I dont think they make them in a seat pressure that high that I have seen yet anyway.

Mine are only 130 lbs on the seat.
My lift at the valve is right around .600.

my 250# figure is a little overkill as mine are at 230# as we speak, I tend to figure a little high for springs as they have a tendency to settle in a bit.

That is true, They will settle in.

But I am unsure if there's something out there to accomodate you if your current requirement is up near what you posted.
I want to believe there is, but a quick search didnt turn up much better.

I think part 265056 from comp will have around 160 lbs on the seat. That was the heaviest one I could find from comp AFAIK. Open was around 400 lbs at 1 inch. I think these figures are based on 1.8 inch installed height.

I'm curious to know for sure what pressure difference between a beehive and straight spring is allowable per given application myself and the ALL reasons why.

Checkout PAC springs. Last time I needed to use a beehive, they had what I needed.