short answer can be done but requires alot of work because you have to lathe down the input shaft to suit the a series crank. not a cheap thing when the input shaft is hardened believe me ive done it with a 63 series dogleg 5 speed. you have to strip the box to get the input shaft out anyway. then there is the bellhousing. completly different, then there is the clutch and clutch hydraulics and pedal completely different ( i had to have a custom clutch made to suit the 63) then the tailshaft and mounts.
but the gear stick is in the right spot :)
basically it would be cheaper to buy an a series 5 speed and im telling you from experience lol
what i did was went to the local wreckers and found a bluebird. stole the whole clutch pedal and hydraulics setup as well at the tailshaft and speedo cable. the grafted that into my 1200 coupe. the tailshaft bolted up to my h165 but realistically it needs shorteningby maybe 15mm.
have a go if you want, it has been done but it isnt a fun job!!!!