things will change, people used to butcher Corsairs to get the V4 for their RO80s, and P5Bs to get engines for their Stags, now the doner cars are probably worth more than their recipiants when fitted with the wrong engines, i mean the RO80 was its engine and with a ford V4 it is no better than an ancient Audi with a transit engine. as for the Rover V8, it may be a very nice engine that in another form even managed to win the F1 drivers and manufactures champianships 2 years running before the all conquering DFV took over, but for some reason the other members of the BL group went to great lengths to keep it out of there cars; Triumph (with the stag) joined together 2 Dolomite engines to make a V8 rather than use the ex-Buic version, and the Jaguars designers when making a replacement for the original XJ6/12 did not maker the engine bay wide enough to take their V12 (so the old XJ12 carried on alongside the new XJ6) because they feared the Rover V8 would be put in there. For the british designers the thought of a V8 in a jag was abhorrent, but then Jaguar was sold to Ford and it got a V8 and horror of horrors i think they might even have put a V6 in them.
Maybe FIAT should never have made the aircooled 126 but instead made a better job of the Bis.