[Arran]

Well the Jensens already came with an American V8 so no need to butcher anything. The earlier ones used a Chrysler 383 and the later ones used a 440 just like my Newport has, though tuned up a little. I believe that most of the drive train was Chrysler, no way a Limey manual transmission would have been able to take the torque so I think they used a 727 behind the Chrysler B.B. Not sure what they used for a rear end though, Chrysler liked using Dana 60s in their power cars for a limited slip but those were live axle affairs on leaf springs. I think that the Jensens had independent rear suspensions, I would have to do more research though.
Interceptors are not as beloved as Jags because they are kind of viewed as a mutt by English car nuts, and are just an oddball make to American car nuts. A Bristol is another British/American hybrid, they started using Chrysler V8s after the pre war BMW clone engines they were building were well past their prime, many used 318s but the later ones used 383s and got a lot more juice out of them then what MoPar did. One exception to the rule is the Morgan +8, those used a Ford 302, that they don't seem to mind, but then again the 4 cylinder models also used a Ford engine.
Speaking of early hemis, there was a French/American hybrid called a Facel Vega that used them, but I think that the biggest engine they used was a 354, many used 331s. Then you have the Italian/American hybrid called a Dual Ghia, those used one or more of the Dodge hemis which were smaller then the Chrysler ones.
Regards
Arran