174?
250?
420?

how to determine what model it is?

Looks like a 250 to me, definitely not a 174

ya, 174 has a different tensioner

yep its definitely a 250 . the kit part number for that b&m efi setup is 155052.

So how much hp gain would it give with a minimum boost on a black 502?

Yep, 250 with their fuel injection. Probably 100-150hp gain on a 502 mag.

It will fit where others won't ,don't see too many of those intakes ,and I may have some pulleys and adjustable fue for the long snout b and m 250 .I wouldn't mind being first in line if you decide to sell the upper and go with a 2x4 carb set up

kind of got the boat with a newly blower install by an engine builder but engine is not completly re installed in boat...
guy owed $ to my brother so hooked it up on the truck and home we went... just wanted to know what model it is so now need to finish install start it up clean it up and... we'll see after what we'll do with that baja 25...

had a 500 efi whipple charged in the 2008-2010 era and ran like 82 mph... curious to see with this one... but it has a bravo 3 drive...