"…for a 4.9 and a 3.3…"
seems kinda fishy to me -
The YF is an excellent 1v. It's readily available used and rebuilt (w/o going to something like this one).
But not very tunable.
Try USA based co.s 1st (Mike's Carbs, Daytona, I 4get the others) some of us trust em more.
(Or back to the pick'npull).
Most folks here rebuild one of them (even if purchased as "rebuilt").
If U wanna upgrade for a 200 (or do U have a 250?) get one from the truck (240/300) but you/ll hafta adapt 'the hole' cuz
the truck is a bigger one (inc the butterfly @base which won't open w/o the change). Double check
the bolt spacing too as I believe that's larger (further) too.
Look to the "Performance Handbook"/u] (hardcopy) or the Classic Inlines (site, just make no purchases there) for more details.
If ur thinkin of a carb switch 1st make sure of what you want the vehicle to achieve/be used for. That will more clearly guide the choice for you…
(sorry if sounding patronizing, not sure where you;re at w/all this).