The heater is not available anymore but this matrix is the main component which gets blocked up or leaks stopping it blowing hot air. This is a new heater matrix for late MK1 plus MK2 cars has 4.5" gap between pipes with opposite outlets for cars up to MK3, which have the outlets fitted the opposite side.
A few Mk1 had 5" gap between pipes which are sometimes available to special order.
See our accessory catalogue for picture guide if you are not sure for other applications.
For pre 1964 cars see 17H5019.