Hi Alan
Another Alan here.....
Here are some factory specifications that I hope you find useful. The first two are for the early 1850 showing both the manual (non overdrive) and automatic gearing ratios.
The second shows the post 76 HL cars specifications showing what they gained over the earlier cars.
Performance figures for the 1500 HL are shown as 0 -60 time of 13.6 seconds, mpg is given as 29.9
For 1850HL we have a 0 -60 time for 11.3, mpg is given as 33.1 (this is a non o/d car), no performance figures for the automatics are given I'm afraid.
If you need any additional info please let me know here and I will see what I can find.