The bestest advise I can give, ALWAYS think things through before you make any cuts. Too many times, I've had to throw away a model, to buy another one, because i DIDN'T think things through well enough. There are several threads here that you may find helpfull in your quest, depending upon what type(s) you intend to convert.
Here's a link to my build thread that has a few Bruder conversions, & more to come.
http://www.rctruckandconstruction.co...ad.php?t=12786
Also you may wish to check out SmallHaul on here. He's the MASTER at converting the small Bruder stuff.
Welcome to our sandbox, hope you enjoy your stay here.