Engine/gearbox ID

I have an ex military 1964 2a the engine that came with it ( not fitted ) has a serial number 95125754E with a plate stating 3/87 date of overhaul will this be the original engine also the gearbox number is 25206917 again will this be the original box with it being ex military will it automatically be different from a civilian one ie 24v or 12v how can you tell ( no clues on the wings ) I'm a complete novice in this area so welcolme any advice or pointers in the right direction
cheers

it unlikey to be the original lump or box if its ex mil. if yer alt is normal size its 12v if its a fook orf huge thing with sheilded cables its 24v

Even if it's 12v, there are detail differences.
From memory, civvy engines have the oil filler through a tube on the side plate, Military engines have a tube into the front plate, which means they have a different water pump (1 less bolt securing it?)
I believe the gearboxes are the same.

Cheers I've read a bit about 3 bearing and five bearing 9" clutch and 9.5" clutch so it's a little confusing and whilst I'm happy to try my hand at most things what I don't want to do is try and fit the wrong bit to the engine or worse spend money on bits that aren't compatable just wondered if I could find out through the engine number which model it was