Question for the team regarding 351C thermostsats

Hello all,

I'm changing the thermostat on my car and have run into a problem that I need some opinions on.

My car is completely stock and I don't think the Tstat has ever been replaced.  Some time ago I purchased the correct 180 degree Robertshaw Tstat along with a brass restrictor plate from MARLINJACK.

When I pulled the old Tstat out, I compared it to my new one, and although they look very similar the "hat" on the top of the button on the old one I pulled out is a bit smaller than my new one:


The two parts I got from MarlinJack fit together with very little clearance around the hat when it is in the hole on the restrictor plate:


I was hoping to not replace the old restrictor plate, but my concern is that if the hole in the stock restrictor plate is too small, then the new thermostat will not open fully when the larger "hat" does not fit into the smaller stock hole.  


Has anyone seen this problem and have any suggestions? Does anyone know how to get the old restrictor plate out of the block?  It seems to be a press fit like a freeze plug and I don't want to cause damage trying to pry it out.

Thanks in advance for your help!



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