You don't generally see that many FFR's with a BB. Small Block is more along the gereral line of thinking for them. Light weight, inexpensive (compared to many others) to build and maintain, good race car, easy to swap parts on. All around good car. I've heard it's "not that easy" to put a BB in one.
IRS vs Live Axle is a another debate all together. My guess is that MOST FFR's have a solid axle. Probably based on the additional expense\mainenance of an IRS system.
Now just because thats the way most are built, you don't have to follow the crowd! By the way, when it comes to FFR it's a really BIG crowd. Probably more FFR's out there than any other brand.
If I wanted a "dedicated" race car I'd go with FFR. For general street/track use I prefer something a little bigger,with more room. But you loose "accuracy" to original specs detail doing that. Hey, you can't have it ALL.
Ernie
EDIT: Heres a link to a recent thread asking the Question:
IRS or Live Axle?
http://www.clubcobra.com/forums/show...712#post379712