Modern day peoples V8

You've already mentioned it, the Lexus V8 is starting to look like the 'new' RV8. Lots of standalone management options, or you can pull the donor car (which you get for buttons) apart and build the whole thing into your project. They're reliable too, even with big mileage on. Not sure how widely used they are in the traditional rod building scene though.

Some rod builders were talking about this at a meet I was at late last year, they get a bad rep because they're not the RV8, or an SBC/BBC, or a Ford. I get the feeling that if they weren't worried about bad reactions from other rodders they would be more widely used, not that they're unheard of. It was a bit funny hearing these guys (you know the type) sounding a bit sheepish about having their feelings hurt by cruel remarks about the non-Yank engine.
I said I'd do it just to curse word people off, they said that's all well and good but they put a lot of time and money into them.

One guy said he liked the mix'n'match way that you can go SBC/BBC/Ford and have a few different 'box options and a few different rear end options and you get to have a unique-ish drivetrain as a result.
The Lexus option, end to end, gives you such a good starting point that you don't need to change much (beyond the manual/auto decision) so you end up with something much less unique.

but arnt these almost impossible to wire up?

I reckon the Audi lump is a good shout... There was a Mk1 MR2 on the 'bay with a 4.2litre version shoved in it, must be absolutely hilarious!!! Wiring would be a pig, but if you are methodical whilst removing all the unnecessary stuff it will be possible, albeit brain scrambling!! Mind you, the more difficult it is, the more rewarding the final result....

I'm pretty sure there is a thread on one of the transit forums about someone planning a jag transplant and one of the tuning guys said dependant on exactly which ECU it was it should be possible to get it running on factory electronics after reflashing (or whatever the technical term is) with a lot of delete options on sensors and immobilisers etc. Failing that mega squirt would do it...

A friend had one for a while and did a few track days with it (before munching the second gearbox) they are unseemly quick for a big luxury car, his was 155mph limited though so you would need to loose that if that's standard and yes I saw it on the limiter (or what it thought was the limit as I had no way to check it) twice

what is comes down to is its still easier and cheaper to source, buy and fit a large capacity american v8, once you get into the management and that to make any of these modern euro/asian alternatives running outside of the donor car.

only this week i bought a totally complete big block caddy with th400, which i saw running and driving before it was removed. the price? £300. youd stuggle to get a lexus engine donor for that. last year i sold a 4 bolt main sbc/th400 from a dayvan for £600. its still quite acheivable to get a decent running complete package for under £500 quid.

also, youre talking huge sums of money to manualise a lexus or bmw v8. far, far cheaper to do it to a sbc or sbf, and most other american v8s.

I don't think anything will ever replace the Rover V8 for usability. Yeah they're not mega powerful but that's a good thing in a lot of cases. You could bolt them into pretty much anything, they'd sound the part, move a bit more briskly but in most cases (and especially in auto form) the rest of the car (brakes, axle and suspesion) could either cope as stock or with minor upgrades.

Start dumping 250bhp and 250+ ft/lbs through most classics and there's a whole lot of other work needed to make it safe and reliable, which greatly adds to the expense and complication.

What about the later version of the RV8 - up to 5.0 ltr available.

That's interesting about the BMW having a seperate ecu, probably why they appear in conversions to smaller BMW's. Just something about the BMW badge that I can't get over!

I'll have a look at the Audi timing belt replacement, I'd have assumed for a conversion doing it on the floor it wouldn't be a difficult job, different story in it's native environment!

I really haven't given the Merc V8 lumps any thought, just a quick flick through Wikipedia and they seem a bit too oddball, and presumably the earlier ones are still cast iron block?