It might be part of the same family (although that link makes it read like it wasn't
the same to me since the new pinto engine would replace it) but I am pretty sure the
deck height is totally different, meaning the blocks are not interchangeable.
I was also under the impression that the 1600 x-flow block had a slightly higher deck
height than the block used in the elans, so while its bolt pattern was the same they
too were not really interchangeable. I'm not fully sure of this, as it is based on
discussions ages ago with a friend who was having his elan S4 engine rebuilt at the
same time I was building my x-flow for the Caterham.
I did a quick google. This link would suggest the x-flow bolt pattern is different to the Pinto:
http://finance.groups.yahoo.com/group/locost/message/9824
Brian, why not try ringing one of the engine builders around london.
I know there is a good ford specialist somewhere near Westerham (build race engines).
I'm sure they'd know, and probably be able to tell you exactly what combination of
flywheel, clutch etc you would need.