Who has drawings from a chassis with a weelbase of aprox. 270 cm? I find it hard to have the angles of the suspension right (castor, Ackerman)

I would not worry too much about true ackerman, the only vehicles which strictly adhere to this are pulled by horses!

Wheelbase doesnt really make much difference to castor angle choice.
In theory, the ideal steering arm position to create Ackermann is influenced, but as the Ackermann principle is flawed by other issues within the suspension geometry, dont loose sleep over it. A lot of modern cars/race cars use very little/no Ackermann....

Many supercars run on negative ackerman to help high speed stability

Thanks for your replay! Measuring my old ford scorpio the ackerman, castor etc. are not ideal according "building your onw chasis" from Herb Adams.....

Think i need to start building ......