I'm picking up my Bv8 Sunday.Its a older conversion with a 62 Buick, Rover 5 speed and stock 3.90 rear end.My friend with a v8 told me the first thing I need to do is ditch the 3.90 and get a 3.07. My question is can I live with the 3.90 or will it make the car a pig.

Welcome to the forum Bob and congrats on the new car!  Be sure to get some pictures up when you get the car.

As a short answer, you can probably live with the stock rear end but it would definitely be a worthwhile upgrade to switch it out at some point in time.  

I would recommend looking through the "How it Was Done" archive and see what others have done with a similar set up to yours.  I bet you'll find that quite a few others have swapped the rear end (or at least the gears).

The Search function on the top of this page is also very helpful, you can find just about anything.  There are several articles that would be helpful to you.

Searchable Archive
http://www.britishv8.org/British-V8-Back-Issues.htm

How It Was Done
http://www.britishv8.org/British-V8-How-It-Was-Done.htm

Have fun with your new car!

I have lived with the stock 3.903 for 5 years just fine, but I have  more overdrive (.63 vs your .80?)  Personally, I would never go all the way to 3.07. Something in between would suit me much better. Then, I would go with less overdrive.

So, it really depends on your driving style.

Congratulations!!!!!!!!!!!

I couldn't agree more with those first two answers, but I would also suggest that you might want to play around with this handy Excel spreadsheet that Dan Masters created: http://www.britishv8.org/Articles/chart.xls - because it will let you see just how big a jump 3.90 to 3.07 is in practical terms (RPM's in various gears at various speeds). You can enter all your variables (e.g. tire diameter) and ponder how your driving style and preferences would be affected. Most importantly though, just enjoy your new car for awhile with the current gear set. If you're used to 4-cylinder MG's, you're likely to find the torque characteristics of the little V8 surprising. It might take awhile to decide...

Thanks for the replies.I was wondering if I would have to drive it like a truck by starting in second gear.

I had 3.7 gears in my Rover-powered roadster with the 3.5 and 5-speed.  I'd thought I'd installed the 3.07 but wasn't aware the MGC axles came with 3 different gear ratios (bought a C axle for the gears).  Car ran well enough with the 3.7 (not much different than the 3.9 would be) but since I've now got the 3.07 gears installed, it's made a big difference.

2500 rpm at 70 mph instead of 3200 with the 3.7.  It'll still pull away in 2nd gear.