Hi Dave...Early engines follow the same layout as the OHV models with only three main bearings. The NF305 is the same bearing as fitted to later engines..the 6305 is a metric bearing (6205 in later engines)and both will be easily obtainable from any bearing factors. The timing side bearing should be lipped...I know Draganfly supply these without a lip (or have in the past at least) so maybe that is where it came from. Again you can get the timing side bearing from a bearing factors.
It is not necessary to shim the crank within the cases, the whole assembly is pulled over to the left against the fixed bearing (6305) when the crankshaft shock absorber assembly is tightened up.
You will need to try and find the correct dimension for the main bearing spacer on the drive side. These can wear and are important in regard to the correct positioning of the crank within the cases...and more importantly correct meshing of the oilpump drive gears.
The drive side outer bearing should be a 'snug' but sliding fit on the mainshaft as the crank must move freely through it when pulled over to that side. Some early engines also had two piece valve guides..these should be replaced with the one piece type.. Finally, what is the problem with the oil pump?...Ian
email (option): ian@wright52.plus.com
Henri / Ian thanks for replys I have no trouble sourcing bearings just was dubious about the unlipped timing side roller bearing.Will fit new bearings and check spacer on drive side to make sure everything is in line then bolt cases together also fit cush drive to check (this is what I do on my B33/WM20 engines) once this is tightened.The oil pump has had a modification it has lost the return pickup & ball and someone has fitted a piece of copper tube in place
. I reckon this is why it also had a horrible alloy sump plate fitted to drain sump regulary.Also the body is badly scoured I have a replacement though just pulled one out of my spare M20 engines.Was told this engine was rebuilt by previous owner, never heard it run though before I got it!!! some rebuild heh
Dave
Hi Dave..People do some very strange things to engines and gearboxes..over the years I've seen it all. Brass shim to fit main bearings in knackered casings, brass shim in small end bushes, bushes made of brass instead of bronze, nails knocked in to take up the slack on scrap crank splines, kickstarts and gear levers welded on, mainshafts welded to flywheels..even crankcases welded together!..I could go on..there seems to be no limit to the 'ingenuity'!! ...Ian
email (option): ian@wright52.plus.com
When I stripped this engine I noticed rub marks on timing side flywheel I now have worked out how they got there,its down to the horrid finned alloy sump plate that was fitted.To fit these you need longer studs someone used allen bolts on this engine and just wound them in.These are to long and have marked the flywheel.Another crap part on the scrap heap,also who would want a magnet near a pickup pipe which attracts all the crap filings!much better to have a magnet on a piece of wire dropped into oil tank from filler cap that you can pull out and clean easily 
Dave..
The replacement sump plates from SRM come with allen screws for fixing them..apart from the question of length there is the fact that stripping the threads in the crankcase is far more likely with a screw than a stud and nut as per original.
The Indian cast version, in this case, is actually better than the English made CNC one..they don't supply screws!
I use them on 'non military' engines, making longer studs to suit. The magnet is easily removed.
An advantage of the thicker aluminium type is that they do not suffer from distortion around the fixing holes as the original pressed ones tend to and it is easier to drain the crankcase if required through the integral plug. However, it should be noted that they are too deep to be fitted in conjunction with a military sump guard....Ian
email (option): ian@wright52.plus.com