I may partly disagree with xlr8or here - I for one would absolutely be up for saving the $$ by doing my own riveting... (depending on how many $$ savings it is of course - if it is relatively inexpensive polish labor and it is critical to getting the car right, I may recant)...the key I think is not having to do any metal panel cutting - I tend to butcher metal panels...it's been a while but I recall having this discussion at ERA - if I am not mistaken, they fit the panel, stick in 1 or 2 rivets (or those cleco pins) to hold it in place and then you take over - in other words - you can't screw up the fitting, but you still do the grunt work.
As for xlr8or's other comments - I agree.
Didn't the original offering on the $24.9F car have a less expensive rear end - still irs, but Ford or something?
Changing wheels to bolt ons, means changing hubs wouldn't it? I think we spoke about this at your shop....this now gets into a lot bigger engineering changes as I recall. Otherwise, if that wasn't an issue, I would likely go with 5 pins - on the ERA this amounts to abut a $2400 savings, but no change in looks.
Along those lines, are Wilwoods not the top end of braking systems? If a good Ford/GM hub could be used, then maybe their brakes/discs as well. maybe this would help to trim out a few $$.