MG Sports Cars

Thought it mite be a good idea to start a new thread on this.
I want to go with a chevy monza rear end .As this seems to be the best one for the midget.Am I correct in assuming that I`ll need one from a 75 -80?
Also are the Buick Skyhawk,Oldsmobile Starfire and Pontiac Sunbird Of the same years interchangeable?
Lastly what do you do as far as the drive shaft?

That's the rear axle I used on my Midget. It's not necessarly the "Best" one for the swap, but does offer some pluses. It's strong enough for a small block V8, has a reasonable selection of gears and posi units available, was used with 13" wheels so the brake drums fit, and has the same lug pattern so no machine work on the axle ends or brake drums is needed. That's handy if later you need to replace a worn brake drum, it's an off the shelf part, no machine work needed.
Yes the Buick, Olds, and Pontiac as well as the Chevy Vega (big axle) are the same. There was a smaller differential axle on some early Vegas that you don't want, but most of the later units should be the same as the Monza axle. Check the rear gears if you find more than one axle, some had better gears if they were from a manual trans car, the automatic trans cars usually came with a 2.78:1 ratio which is a bit on the tall side. If you can find one around a 3.08 or so it will be much better. Later model gears can be used in that housing but the pinion shaft diameter will have to be ground down to match the early style pinion bearing. Not a big deal, my machine shop only charged me less than $50 to do that job when I changed. You might also find some positrac units in these cars, go for it if you find one.
The drive shaft can be made from the Monza shaft or the one from the Camaro. The U-joints should match, if not I bought a custom u-joint at the local drive shaft shop that had the small Chevy bearing caps on one side and the larger caps on the other so it would adapt the early size small u-joint to the later yoke. That's what I had to do when I installed the Camaro gears, had to use the Camaro drive shaft flange on the rear and needed the conversion u-joint. I gather it's a fairly common piece because of all the Chevy engine swaps over the years.

Many thanks once again Bill.I have had no luck as of yet finding any of the above mentioned rear ends.
I did see that a 8.8 out of a ford ranger may work?Are there any other newer ones that mite be a bit easier to find that would fit the bill without to much work?I Really don`t want to shorten one unless I half to.Was thinking I would try and flare the fenders and if a bit of the tires still stick out then what the heck.

Mike, there's nothing out there that will fit as is, any stronger rear axle will have to be narrowed to match the original MG Midget rear width and spring perches fabricated. That's just the nature of the beast. That particular rear axle is going to be difficult to find as it's getting pretty old and most of these cars have met the crusher long ago. Yes the Ranger rear axle would probably do fine, but it will need to be narrowed. Make sure that the brake drums will clear a 13" wheel if that is what you will be using, some later rear axles with disc brakes might not. You'll either have to have the rear axle flanges drilled to match the Midget lug pattern and possible have the axle center hub machined to fit the wheels as well or consider custom wheels with the Ford pattern and change the front hubs to match. For me it was simpler to keep the Midget pattern as I already had the wheels I wanted.
One thing to check for any rear axle is the diameter of the axle shafts where the new splines would have to be cut. Most axles taper down and then back up near the end next to the splines. When narrowed the new spline area often falls in the necked down area and you either have to have the axle built up by welding or have a new axle shaft made from scratch, which is best. In the case of the Chevy Monza rear when narrowed to fit a Midget there is just enough material at that point on the axle to allow resplining saving a bit of money. Add that to the savings not having to have the flanges and brake drums redrilled and it's probably the cheapest rear for this swap there is if you can find one. Be patient, I see some Monza parts every few weeks on craigslist in KC, they're still out there. My second choice would be the rear from the same era Camaro the engine came from or the S10 but both would need axle drilling for the 4 lug pattern. At least the rear brake cylinder bore is compatable with the stock Midget master cylinder so no changes would have to be made there. That's another factor that some forget, rear brake bore compatibility with the master cylinder. Get that too large and you'll then have to have them sleeved or go to a dual master cylinder and balance bar arrangement for the brakes.