Hi David.
Well done. It is a great feeling when you make great leaps in the build. It starts to feel like a car when you fit the engine rather than a trolley!
I'm a little confused with you ECU issue. Do you mean not long enough to fit to rear bulk head rather than dash? If so, you could mount a piece of ally sheet between the upper and lower chasis rail under the battery try. And fit it onto there. I also had a good find with the ECU. If you look under the bonnet of some 800 turbo's, they have a nice arrangment for mounting the ECU. With the relay pack. If you look under engine start section below.
http://www.kitcar.good-hosting.co.uk/
It's funny you posting about a great milestone fitting the engine. I'm doing the opposite this weekend and taking it out!