I'm in the process of feeling my way through a build of a second MGA 1500 engine from the pile of parts that came with my car. I'm finding that I can actually make progress by tackling one component at a time.
First was the rocker arm assembly. I had 2 sets of rocker arms. Both shafts were shot, and one set of rockers needed bushings. I used spacers instead of springs and now have one good rocker arm assembly. (The one that is now on the car was originally gaped to about 0.24" and was very loose, and contributed, I believe, to a misfire problem I was having.)
Then I rebuilt the head. Since I'm going for a race engine in theory, I spent about 40 hours porting the head (I wonder how that will turn out!). Up-sized valves and 7000 rpm springs. Pretty much finished, just some time to add the manifold bolts and the thermostat and cover.
Next up is the oil pump. Assuming I can use what I have, I will try to increase flow capacity. But then that will be done.
Then I plan to make a windage tray for the oil pan and get that welded in. That will not be a properly baffled pan, but should serve the purposes of this engine.
In the meanwhile, I am slowly assessing the block. Some of the connecting rod bearings are gouged, indicating dirt in the oiling system, but some other bearings seems to show evidence of oil starvation. So I have to figure that out. Probably have to open up the oil galleys (which I was trying to avoid), clean them out and maybe open up some of the oil passages in the engine. It took me a while to figure out the pistons. It appears they are 6 over 1600 dished pistons, giving the engine about 1640 cc. Now that the head is done, I'll figure the compression ration and perhaps order up some flat topped pistons. Then I have to figure out the camshaft, which seems too mild for this block.
In any event, by starting with the peripherals and breaking the job into little segments, I'm finding that I am not so overwhelmed with the project. Good luck with your build.