Build a 528 or 543?

I have a couple thoughts here... First, on the block choice... You will be doing significant work to get a factory block to run at this level, and it will definately give up and be junk in a shorter time. If you want consistancy over many years, you are MUCH better off with an aftermarket block as you will be prepping a second block eventually, especially if you race year round and every weekend. The engine you're talking about building is a $10,000 package at least. So spending an extra $2K on a real block might make sense. You're going to spend at least $3500 on machining and reinforcing parts to get the factory block ready to run at this level. Second, I dont see a 4.375 kit for the B wedge block... They have the 4.25 stroke with the B length rod, but my first choice would be the 4.15 B kit. You have what I'd call a heavy Glide car with mild gearing. You want a relatively flat torque curve, and low rpm. You'll need a new convertor anyway. The head packages you note are good for the 4.15 stroke, but I thinh you'd need more head for the larger choices. Stay with the longest rod you can, run the B block for longevity, and keep the heads that you mention to keep the torque up and the peaks flat.