if your running ICS, SCS, or HIC it can interfere with the starnut(ICS) or the topcap which needs to be above the top of the forktube, if your running threaded you should have no problems
The headtube on an MGP is shorter, so you can either cut your forktube or use spacers to make up for the missing headtube length. Otherwise there will be too much oh the forktube coming out, and you won't be able to use SCS or HIC. You can still use ICS fine without spacers, just hammer the starnut in further.