G'day Dawso, my method on those is to punch the pin through into the chassis and then "walk" the clip out. Works most of the time & you just go to a bearing place and buy some nylon rod & cut into lengths to make pins. Old fashioned people use knitting needles to cut up! But saying that the clips arnt very dear, & old ones might be brittle. Theres probably other methods, and panel beaters would just chisel through them

see how you go

cheers
Max