Wading through the funnies here I don't think anyone has mentioned the interior differences. When I was doing my due diligence before buying, both SPF and BDR were on my scope as were a few others. I wound up going to the London Cobra Show back in 06 just to look at and try on a number of manufacturers. I highly recommend that show BTW. Being one of substantial size and girth, how the interior fits me could have been a deal breaker and as it turns out it was. I sat in quite a few cars and it went something like this:
SPF with no mods = No way for my fat azz
SPF with "Big Boy" mods = OK but still quite uncomfortable
ERA (don't know mods) = No way
FFR (don't know mods) = No way
BDR No mods = Mmmm, maybe so, not bad at all
BDR With chubby guy seat (thanks ROUSHAC!) Aaaahhhhh, this is it!
There were many details of the SPF at the time that I really liked, such as the 8.8 rear, but ultimately I just didn't fit into an SPF and bought a BDR from Jay at Vintage. I haven't looked back since.
Steve