Windsor Jr Heads On A 351.

My b cam was so powerful it teleported my car right out of the garage!

Thor has his hammer while I can hold THE cam of all Camshafts. Mere mortals can only bask in its brilliance....

They flow on par with GT40/GT40P iron heads... around 200cfm at 0.500 lift.
Take them up over 0.600 and they flow ~230cfm... but doesn't sound like you want to cam it, so, with ~0.450 lift... ya...
With a some port work and decent valves they will go 260ish cfm up around 0.600/0.700.
I would expect handy 280cfm out of a set if you had the money (think $3000.00 labor alone) to have them done right.
I though long and hard about running a set done right... but stuck with the stock heads (equally labor intensive for about 50 less cfm, but hey they are "stock" heads right?)

As such, without doing a bunch of work to them and going pretty aggressive on the cam and addressing the low compression of the truck motor, you should expect GT40 iron power... especially with the "GT40" intake and stock cam. I'd say 30hp is fair, if not fractionally optimistic.

If you want a good iron head, search out a set of old TW iron high ports... good luck finding a set.