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www.madefi.com
only place I know, they also have a few good parts for your v4 looper

Omc sst100 is the bench mark there and that was just a stock 140 unless you have a T2X?

The early 70's v4 race motor
Had 8 barrel carbs

You might still have rules in the mod to keep it sensible like no sleeving under original and only stock crank stroke etc
Maybe even stock looking powerhead?

the original OMC 140 at 1800cc has the most potential HP at that capacity class
what mods does the class allow