Inspecting the differential

Next on the list for appraisal is the differential, it is documented as a "D Type" they produced three varieties of this particular type shown below.

Unfortunately I don't have a crown wheel so I cannot identify the part from measuring the ratio. I have an image of the internals missing the crown wheel.

The unit looks partially restored but missing the Crown wheel and matching  pinion. I have 4 x 18" wheels I guess that may set the ratio in the end. The rear brakes, hubs and back plates are also missing.

 Here is an Index page for the build

Update 27th Aug 2015

I costed a new crown wheel and pinion for the diff and the hubs and concluded the cost would be in excess of £800 to continue with what I have. I managed to pick up a very good second hand part from Tony Betts, the above item will go on ebay eventually once I make sure no other bits of it are any use. The ratio of the unit I have purchased is 5.125:1 and with 15" wheels would give a top speed of 67.4mph at 5000rpm or 75.5mph with an 18" wheels. For my application I think 15" wheels is what I need. However road legal competition tyres could be an issue unless I go to 16".