There is a car up for auction next month in Glenview Illinois identified as
a 1950 Edwards R26, with an early XK engine. The auction site does not give
the engine serial number, just mentions the number D628 stamped on the head.
It is a studless head with short top SUs, coil mounted above the front carb,
6 blade fan, which would put it in early '52, and it has an XK120 top water
hose elbow, not a Mark VII elbow which would have had a thermostat. The car
has Smith’s speedo and tach, possibly also a Moss box and Jag rear axle.
Sterling Edwards built this car in 1949 and raced it in California for a
couple of years but it had a Ford V8. I could not find anything about how or
when the XK engine came to be in it. Being a race car I suppose it got
modified a lot in the first few years.
http://www.auctionsamerica.com/events/feature-lots.cfm?SaleCode=LH11&ID=r115
http://www.96trees.com/edwards/edwards.html
BTW in the last link we see that a Mark V saloon made the cover of the
January 1950 Motor Trend.
And for a good laugh scroll through the other cars in this auction to the
1950 Veritas.
Rob Reilly - XK120 FHC & Mark V saloon