I only do basic math, no multi-variable calculus for me.
So, here's a brand new RHD Gulf SPF GT40 in Hemmings asking $134,000. I assume it's fully optioned with the RHD and Gulf paint.
http://www.hemmings.com/classifieds/...0/1774884.html
Add: $10,000 SBF engine
Add: $10,000 ZF transaxle
Add: $10,000 Olthoff install, parts & labor
And you got yourself a brand SPF Gulf GT40 for roughly $160,000 more or less. You can certainly spend more (or less) on a SBF. And you certainly can spend more (or less) on a transaxle.
Or you can buy a used red SPF GT40, assuming it's still available, for about $130,000. A seller can ask whatever they want for their goods, that's America. But only when a seller becomes motivated, will a deal be struck, often, substantially below their ask.