OK, now I've heard of folks doing that, but theres alot of stress there. Its a matter of how much 'fudge factor' you need. That, my friend, is a cheap way of getting around 'being exact' as far as lineup goes. B&M, Holley, etc. land all over the place, and can get by with this where if you have a Gilmer or 'cogbelt' on a Roots, if you don't have things just so-so, if your tracking hard to the front or the rear with your pulleys, and you have faceplates on your pulleys, they're gonna fray really fast, its gonna start having 'babys', and those 'babys' will grab your wires, radiator hoses or anything else thats close by and tear them to hell.
On the grooved rib-belt, as long as you can get a long straightedge, put it along side the edge of the blower pulley, both front and back, and your pretty well centered on your crank pulley, yes, you can run it. Me, I ONLY run same size top and bottom, and have things lined up. I don't let misaligned shit leave my shop
But, I would call B&M, to be on the safe side, both the 144's and the 177's still have alot of pull on them when the boost is on. If your blower belt is too narrow, you can get slippage, your belt will heat up and could possibly lead to failure. Blower belt failures have taken out whole nosepieces before, not to mention hoses, radiators, rad. mounts....
It would be best to call them, they can tell you the correct belt width and dia. is for your app, what your bottom pulley is supposed to be dia. wise and width.
I have all kinds of reference books on these things, I've had some of my customers buy used kits and be really over-driving the blower for their application. Its best to call and give them the blower #, pulley dia.'s, motor size, all that info. Because you don't know if the guy before you didn't replace the top pulley, going from 1to1 to 10% over, or more. I've run these little buggers at 30% over, really cranking the boost, but keeping motor revs down.
All it takes is a little too much boost, to blow out your head gaskets at least, at worst melt down your whole mill or just break a crank and some rods....