As mentioned above, it ought to be a fairly straightforward conversion - CVH cars like mine, a little later than yours, had the Ford type 9 gearbox as standard, so all the bits should be readily available from the usual suspects.
Mine's still a cable clutch, though. Not that that worries me unduly - the one time the clutch cable broke while I was out on a run, I was able to putter along in 2nd gear and make it to a supermarket car park on the edge of town, from where I got a ride to a parts supplier who was able to find a Capri clutch cable of more or less the same dimensions, even in the 'wilds' of suburban Southern Ontario... a bit of judicious bodging with extra nuts and penny washers later, I was able to drive home.
If You can make it work easily, stay with the easy way. On a trip to the "Lost Coast" of Northern California I ran over some tree limbs. These limbs got jammed in the hydraulic lines of My internal clutch slave, cracking a fitting. I was able to make it back to Seattle, but had to pull the engine twice to fix it. I could not see the crack nor could I see what was going on because of the bell housing. There are downsides and upsides to this conversion.
