Hi,
In case you just check, you’ll find that I went through the same process only 2 months ago (In the process of buying an XK120 FHC - #39 by LLuis_Gimeno).
I bought a matching numbers car (except the head), that happens to be in very good shape. Although I cannot of course be sure that someone re-stamped the block, chassis and gearbox, everything does seem original.
For me the decision was in part similar to yours, I had three further candidate cars fitted with MkI, II and MKVII engines. The one with an MkI engine was incredibly fast. But now to what matters:
- Body and Chassis wise all cars were exceptionally good
- Mechanically all cars were really good (I did now more than 1000Km in mine, no issues, but lots of preventive maintenance
- Steering and brakes are really good in a XK for anything that normal traffic can give, really much better in any case that what even reputed classic car journalists write.
- No overheating what so ever
- Final Drive is short for modern-day highways and the torque of the XK engine. The 5-speed is an option, but it needs chassis-cutting → Why not try a longer final drive (2.88) in case you go for an original car? It would bring 2200rpm / 100Km/h instead of 2800 rpm, which I admit is boomy.
BEWARE or thinking modifications before you own the car. At the end I am really glad I waited. The only change I did (other than an Aluminium radiator for no real reason) is the 123 ignition (and yes, I recommend, from 3800rpm at least in my case it has noticeably improved smoothness).
Buy the best car you can find, matching numbers will inevitably fetch higher values, also longer term, but I would certainly not have bought a matching numbers car in need of major work, rather a well-appointed non-matching, in my case it’s just that I found a matching-numbers that I liked.
Best,
Ll.