What you write makes perfect sense to me. I paid 450 for my car, plus 452 for immatriculation (the charge is based on fiscal hp in France, mine is 22CV) and then spent nearly 50,000 to build my car (but delivery charges and duty/VAT account for a big part of that cost, that a US-based builder need not worry about).
Differently from you, my son and I decided to retain the slant-6 engine but found performance parts for the car mostly from Australia. I ordered the cylinder head and other parts from "Hemi Performance", located near Brisbane. Other helpful sources are "AussieSpeed" and "Pentastar Parts". Here are some links..
http://www.aussiespeed.com/
http://www.hemiperformance.com.au/store2/p_889_Slant-6-225-Standard-Performance-Crate-Engine
http://www.pentastarparts.com.au/
AussieSpeed has a US presence and Campbell Enterprises (very friendly and helpful people) also provides some performance parts for the slant-6.
http://www.campbellenterprises.com/
Hemi Performance offers such interesting solutions such as a ported, polished and gas-flowed cylinder head with larger valves and dual valve springs, triple Weber DCOE45 carburettor kits, a fuel injection kit and much more.
My the engine of my car has been bored slightly, for a displacement of 3.8l, has high-compression Wiseco pistons and connecting rods, a mild racing cam, an AussieSpeed equal-length runner intake manifold with a 360cfm Edelbrock 4 barrel carburettor, as well as a tubular extractor from Hemi Performance. The exhaust system is a 2-1/4" builder's kit from Magnaflow.
Planned upgrades include an aluminium performance radiator from Smith's Radiators and, perhaps, an engine oil cooler, links for which I provide below ;
http://www.smithsradiator.com/mopar/abody/index.html
http://www.andysautosport.com/oil_c...sb_price=Sort+by+Price&sb_brand=Sort+by+Brand
I also have an NOS nitro system installed but have yet to test it.
In any event, a performance slant-6 is fully possible. It just requires more research than a V8 solution, but probably is no cheaper than a swop.
I believe my slant-6 is good for roughly 300hp and sounds quite awesome, especially with the exhaust cut-off open. The Ford 9" rear axle was provided by "Control Freak Suspensions" (who also provided the front axle conversion). It has a "Strange Engineering" limited-slip differential and 4-wheel "Wilwood" disc brakes.
