A Holley one should fit they are the same size as the carb. I'd go for the cheaper Sniper since it'll be hidden anyway. Check with Craig Conoley to see if anyone has done it yet.
Paradise Wheels, Inc. is the exclusive supplier/manufacturer of all ball-drive McCulloch and Paxton superchargers that were made from 1950 to 2000. We manufacture the original 1965-1968 Shelby GT350 Paxton supercharger kits that were available from Shelby American in 1966 to 1968, and all parts are available separately. In 2000, we purchased from Paxton Automotive all rights, inventory and tooling for Paxton centrifugal ball-drive supercharger units. In addition, we offer parts and rebuild services for all Paxton ball drive units (SN60, SN89, SN92, SN93 and SN2000), and McCulloch VS series units.
This listing is for the 1965-1966 Shelby GT350 Paxton supercharger kit. This kit will include all the necessary parts to install on your HP289, except a modified blower specific Paxton carburetor (those are available separately).
It is possible for you to modify your existing carburetor to work with this kit. I recommend a Holley 650 double-pumper 4150 series carburetor, or an Autolite 4100 carburetor. These carburetors are available separately for an additional charge.
https://paradisewheels.biz/