You guys are probabbly right, a 4:11 which means Ian will see 3,000rpm@45mph as in my S5 1300. I was just thinking that maybe the later 1600 saloon had 3.54 on the LS & GL then a 3.70 on the GLS for acceleration. So if I assume the wagons were one step down, a GLS Series 8 on would be at 3.89:1.
My Chrysler '76 brochure states the 1600cc (S6 MK1) had the 3.70:1 and I notice too an article on the 1976 1600 Super, which were the last Supers before the MK2 and had the the round headlights, they had noticed a higher top speed and better economy than on the 1974 1600 they had tested.
The '74 Avengers photographed in Brighton' states a 3.89:1 ratio for the 1600, this being a S4 then S5 got a steeper static timing curve, they upped the 1300cc to 4.11:1.
Looking at the orange 1600DL Avenger I came accross whis is a S5 (service#, Sunbeam type window handles and concave front struts) it had 'T5xx' in the Service code which apparently means HC and 3:89:1.
Anyhow its seen that there were a lot of changes made even to the MK1 Avengers throughout its production. This is unusual for cars of the era, usually they started bad and got worse! It can be tricky getting the correct strut inserts for them with all the changes. S5 (09/'74 on build) got concave struts then also the strut for a drum brake hub is diffrent again.
For example, 4-door 1500GT had 75bhp, the 1500GLS had 78bhp, the diffrence being the holset fan the GLS and 2-door 1600 GT's got.
Morris Marina owners need not have to think about such details!