I'm looking for a cap that is 15,000 uf 80v, 85c 35mm wide 80mm tall 2 lead 10mm spacing. Now those as the min space I have room to go up to 105mm tall, higher voltage to 100v and higher 105c temp. I can't seem to find these caps. But I know there out there somewhere.

 

While not in stock at Digikey, this cap matches your ratings and size: (82mm high)
ESMH800VSN153MA80S
There are variants with higher capacitance, but most are that same size.
Good luck finding one...

 

So I have found out that stock spec is 100v 8200 uf 35mm wide 80mm tall 85c temp 10mm lead spacing. But I have opened 3 of these amps and every one has had 15,000 80v main rail caps. Not the same brand but same spec. I have always been told u never downgrade the voltage spec. How could this be safe?

 

It depends only on the voltage. Transformer rms voltage *√2 gives the peak voltage. Add the transformer regulation percentage. Add 10% to account for variations in mains voltage.
The capacitor needs to be rated more than that. If 80V is more than that, than an 80V is acceptable.
The original capacitor may have been 100V simple for expediency - that might have been what was in stock.

 

I have looked and looked for stock 8200uf 100v 35mm caps. Can't find them anywhere even mouser or digikey can't find them. So I ordered chemi-con 17,000 uf 80v. Small upgrade from what's in there now with the 15,000uf 80v. The way I look at it brand wise never heard of hec caps but I know I can trust chemi-con brand of parts.