SBC9248PRO progressive linkage for 2-2 barrels

[pete rose]

Hi Fellas
I'm trying to find a progressive linkage for my
59A engine. Isky 2-2 barrel intake, dual 97'S
Max1 cam.Carb spacing is 5 1/8 inches
Currently running straight linkage and would like to try
a progressive set up.
Stromberg shows SBC9248pro at Summit and Speedway
both are back ordered and future shipping dates keep moving.
Sent a message to Max at Stromberg in Salt Lake several
days ago and no reply.
Does anybody have a suggestion for an alternative?
Also any thoughts on progressive set up are appreciated
Pete Rose