Can anyone advise me what sierra master cylinder I need for my Cortina front , escort mk1 rear brakes? Also, does anyone have one for sale? Thanks.

The standard Sierra master is usually OK however if you want to work out ratios you need to find out the master cylinder bore, the pedal leverage ratio, the Cortina front caliper bore and the rear brake cylinder bore's.
In practice any Sierra master cylinder will be OK, the drum rears will give enough braking but not to much for IVA. i.e. it will pass the IVA brake test.
If after IVA you find the brake balance not to your liking you can put in a bias pedal box and set it up to your taste.

For IVA you only need to provide balanced presure to both sides of an axle and very importantly not lock up the rear brakes before the front, unlikely with rear drums.

[Edited on 16/1/10 by snapper]

Sierra master cylinder is not the best choice it is designed for use with a servo and pedals with much more leverage than available in a 7 style car, the result will be you will have to use all your weight on the brake pedal in an emmergency stop situtation.

You should try and pickup a master cylinder from Fiesta Mk1 basic model without servo which has a smaller bore which will reduce the pedal effort to acceptable levels.

Fiesta cylinders can usually be found on ebay.

A Sierra master cylinder without a servo in a car weighing 1200kg's would require a good deal of effort to produce the desired effect.

Using M16's at the front, Capri drums at the rear and a Sierra MC gives just about perfect results, so much so, the tester at SVA commented on how good the brake feel was.