Yes, you could do that, they should come out with a little heat if you're referring to the Magnus factory installed screw in heads.
Your heads are advertised at 85 grains without adapters but they are probably a smidge over that.
The only catch is the heads you have are 5/16", as far as I know all the steel adapters available are 11/32". You can still use a steel adapter, but the heads will not seat down on them as far as they currently are. With the 75 being a short adapter, I'm not sure you would have the amount of contact area you want.
You can see our adapters here, it should give you some reference:
http://www.braveheartarchery.us/new_page_4.htm The 75 grain is the shortest black one.
Hope this helps, Tim