i don't think any of the aftermarkets have the offset t-stat besides the performer. and i know that the performer is the only one that's got the provisions to mount the compressor bracketry.
with an aftermarket bracket and the shorty compressor the weiand twins fit no problems.
I remember reading that Dave Hughes said he could get the performer manifold to flow the same as a stock rpm ag with his stage 2 deep porting.
I think i remember this work being around $350.
Not sure if he is doing this work anymore. I think he is just mostly selling parts now