Looking back, a lot of us got backed into the replacement type (SR,440-1,Eddys,etc) simply because they fit some of our parts OR, were familiar. A B1 seemed out of reach at the time because it required going the whole way. New pistons, valvetrain, intake, the whole topend plus pistons plus drain lines, ETC. Forgot to mention a converter change would also probably be part of the change. Add $1200 to the changeover. Advertising made a huge difference as well, and the Indy stuff and Edelbrock stuff well promoted.
If you look at what can be done with a well worked 440-1 or 572-13 they make more sense for a 500 to 550 inch street motor because the torque peak is about 1000 rpm less on a 528 cube motor. A 440-1 will peak about 4900, B1 5900? So to my thinking the B1 is better suited to a huge(by yesterdays standards)street motor, 572 and up. Sure you can make the B1 run OK at 4500 rpm with a 500 cube motor, but the smaller port motor will pull harder there. I am still hoping someone with real world experience on a flat tappet/B1 combo would chime in to show what could be done on a smaller budget. With a 541 cube stock block, B1 heads and a big flat tappet cam, I would think that combo may have an edge over the Indy stuff within the range of the flat tappet cam. Specifically the Comp 650 lift, 290 cam. You can get by with the standard B1 rockers, the cam is cheap, and should rev to 6800 reliably.