Alpine window template to fit interior trim?

Hi everyone,

I just bought a 1985 Defender 90 with the basic roof and want to put some alpine windows in but I can't find proper measurements to install the windows and then have them fit with interior trim. Yes I have done a search but the people who have cut out windows before didn't do it to exact interior trim measurements and I want to be sure before I start cutting anything. Anyone know where I can find a template or have fitted interior trim to retrofit alpine windows?

Thanks