I've done migration from linux to OpenBSD. They have got a lil bit different syntax in /etc/passwd file. Make sure you check on that. Everything else seems to me just fine with your algorithm.
I might be mistaken but how can you run 75 httpds on separtly on one box? As far as i understand you run just one server and it creates child process using config file. If this is the case then you just have to install just one httpd and edit and copy your old httpd.conf to a new box.
Regards