Please restore the original - don't turn her into a muscle car
Well, it depends on what you mean by "original" but my plans are to toe the line on something that LOOKS right.
First of all, don't worry, it won't be a muscle car. British sports cars like these were never meant to be fast-they're for carving out the twisty roads. With that said, I've done some very basic work to boost the power of my MGB, and it's welcome especially when you're doing something like pulling out of a curve.
The MGA above(that I own) doesn't have a complete engine-it has a block, head, and a few miscellaneous pieces.
So, with that in mind I've sourced(but haven't bought) an engine pulled from a 1963 MGB. MGB engines were 1800cc, while the largest MGA engine was 1622cc(mine was 1500 originally). They are the same basic B-series block that was a BMC corporate standard engine used in hundreds of different models. The first couple of years of MGB engines used 3 main bearings, like the MGA engines. Later years added two additional bearings. The "3 main" engines are desirable and are described as "free revving" as compared to a 5 main engine.
The 3 main engine will get an AH2923 head off a 73-76 MGB. This is what's known as a "big valve" head, but more importantly it has a smaller combustion chamber volume and raises the compression ratio of the engine from 8.8:1 to 9.5:1. I just did this on my 1970 MGB, and it's a night and day "seat of the pants" difference.
I'll send the head off to a friend to port and polish it. Then, the engine(after boring the cylinders, line boring the bearings, etc) will go back together with an APT VP-11 street performance camshaft.
When it gets dropped in the car, it will have the backplate and flywheel from the original engine in the car to allow it to mate to original MGA transmission(rebuilt). I'll lighten the flywheel a bit, but that's it. It will get the SU H4 carbs(rebuilt) original to the car(I have them), and not HS-4 like an MGB(and certainly not a Weber). It will also get the original Lucas 25D4 distributor with points, although rebuilt and recurved for the engine. I intend to put the original dynamo on the car and wire it positive earth, although admittedly an alternator and negative earth may win out in the long run.
So, that's my plan for the car. Is it original? No. It will, however, increase the stock HP of the car by well over 50%, which will make a significant difference in driveability. Also, even most MG nuts wouldn't notice the changes.