ECE 4/6 Drop Kit w/ BBC?

[Tcal]

I was going to order the 4/6 Drop Kit from Early Classics this weekend (They're having a 10% off July 4th Sale!). I tried calling their number, but evidentally they've got the placed locked up for the 4th.

So my questions to you guys:
a) Does anyone know if their front springs are sturdy enough to hold a Big Block?
b) How much will a BBC add to the 4" drop in the front?

Thanks in advance guys!