I don't think its unrealistic, the rest of the car is set up right. I'm not sure the .528 will get you there easily, but it should get you there. It may take a big of tuning. Its a good cam, but not a big top end screamer type. It'll be a nice street/strip setup though. A 509 would probably get you there a little easier, but I'd try the .528 since you have it. 12.50s is probably what I would expect from that. You should certainly be in the 12s, it really just depends on how sharp you tune it and how tired the 400 is.

EDIT I see you don't have a cam. I'd run a DC509 (old one with 108 LSA, in at 102 or 104 ICL), run either the 452s or the 516s. I'd run the 452s, have them milled as much as you can. If you want give them a shot at home porting. I think it'll run strong though, the car is set up well with that converter and gearing.