The non-equivalencies of the 'metals' aside, Marriott has tended to do more challenges in recent years and I have heard of few successful 'matches'. There is an active thread here for reference to challenges.
There was also a Road To Platinum/Gold etc. program, but I don't know if that is still running or not. I have heard various reports.
If y ou have 50 nights, the requirement for Gold, you are only 25 away from Platinum at the most. Were you trying for the incremental improvement in points for a planned stay?
Spend some time researching. Some programs only only a match *once* per lifetime of the individual. Unless you are staying at a Hyatt, the match doesn't really do anything for you, and if this is a once-a-lifetime match, you might wish to save it for when it counts, and when you have a higher status in a program to match in the first place.
I asked similarly about a Marriott to Hyatt match on Flyertalk and was told it's easily available but once in a lifetime. Since I only had one stay planned and theres only 2 or 3 Hyatts in the UK I gave it a miss. Hyatts top tier us well worth its place, but I need to be able to squeeze it properly if I'm to blow my once in a lifetime match!