Having been through exactly the same questions and processes myself I think the best thing you can do right now is follow the advice that G-o-g-g-o game me: order a Parts List book and workshop manual from the Heinkel Trojan Club. The parts list has drawings ("Exploded Diagrams") which show how all the small parts fit together to make, for instance, the handbrake assembly. These two books are essential for anyone restoring a Heinkel or Trojan, unless they have a VERY good knowledge of the cars, and believe me I had no knowledge of them when I started, and I did not understand why G-o-g-g-o was so insistent on me getting the parts list......until I did!
Most Heinkels and early Trojans have a long horizontal internal"sill" running along the side of the car which forms part of the hand brake bracket assembly. My Trojan does not have this, mine is a "floor plate" with 2 upright plates and the brake lever and clutch mechanism fit between these, I would photograph it for but as mine is probably different to yours it might not help.
There is one thing to watch out for WHEN you get your parts list book! Early Heinkels had a rod gear change mechanism, a smaller rear cowl over the engine, and various other differences, so you will have to interpret the book somewhat as it covers early ones. Trojans were further stripped down to cut costs.
It seems to me you are at a crucial stage in your project which I recognise, having been there myself! By the sound of it our two cars had both declined into a VERY similar condition, almost a point of no return. Despite not being very knowledgeable about cars I persisted. I had a lot of good advice from G-o-g-g-o which I heeded, and I did look at his and other owners' cars, and also looked at the Members Area at
www.heinkel-trojan-club.co.uk , this is very useful, as indeed is the members Handbook which contains a lot of information which makes a restoration possible. You really HAVE to get these publications or you will be forever banging your head on a wall, and you will give up, thus wasting all the time effort and money you have already put into it.
I acted on G-o-g-g-o's suggestions and advice, and now am the proud owner of a car, which although unoriginal, was still nice enough to get 2nd place at the National Micro Car Rally in 2007, and it causes a sensation wherever it goes, getting more attention than Lamborghini's and Aston Martins!
