I'll post some pictures of my Chev unit when I unload the trailer and show how the linkage works, the inboard butterflies open first to about 1/3 open the outboard side opens and they both continue to WOT. I have some more 97 bases that I'll split and post photos.

'45 Ford PU
66 Valiant wagon, leaning tower of power.
79 Chevy C10 w/250
02 PT Cruiser Convertable