Does anyone have experience with this offenhauser 2x4 intake ?

The 5488 comes up as a '64/'65 only (different bolt size and angle than '66 and later smallblocks) 273 (small port) intake. Still available new.
The 5497s are just universal "cross ram" adapters that they sell to convert a standard inline dual quad into a quasi-crossram. Also still available new.
Ran a similar Offy inline for the '66 and up 273/318 years ago with dual Comp Series Carter 500s on it- performed okay, and street drivability was surprisingly good, but I wouldn't say better than a well sorted single four. Looks cool, though!
BTW, I didn't have the crossram adapters, just the manifold; so I can't comment on how it performs with those on it.