what year is your car? if it is pre 74 you will need a post 74 engine cross member to mount the a15 (or make adaptor plates)

if your car is pre 74 you will also need to rewire the alternator to the other side of the car

you should use a15 inlet and exhaust manifolds, the carburettor is essentially the same

the fuel pump is also different to pre 74

the distributor is mounted in a different place but the unit is the same

the clutch cable may also be different (different diameter mounting boss where it passes through the bellhousing flange)

the a15 is 10-15mm taller