Saving Old Seagulls

Obtained a forty minus (SJM 303B4) earlier in the year with a seized engine and gearbox, stripped it apart months ago and left the power head soaking in diesel and managed to un seize the piston in the bore, pulled the cylinder off the crankcase and found the rings stuck but have managed to release rings in grooves.
Problem is with the gearbox now and its the first 40 minus gearbox i have taken apart so not sure what parts are supposed to be in it, think someone else has had it apart before as the thrust washer shim on the prop shaft behind the bevel gear is missing if its supposed to have one and the screws were not tight as usual. Have also found that after drifting out the pinion assembly from the gear box casting that there is no split pin or washer holding the assembly together through the pinion and does not seem to be a hole low down the pinion shaft for this purpose but there is a hole near the top of the square drive part.
Can any body tell me if there should be a thrust washer shim between the bevel gear and the front gear box bush/plain bearing , and also if the pinion assembly is correctly assembled like this

There is usually a shim fitted, to allow gear meshing to be adjusted, there are several sizes available. Well done in getting the pinion out, that is a bugger of a job!

Once it stated to move it wasn't to bad to drift out, trying to use a drift on the angle wasn't the best but the only way i suppose. Will have to get hold of the shim once I measure the movement in the shaft. Thanks Oyster 49