Engine Help cooling issue

Ok new to this so I hope I’m doing this right
I have a 91 fox with TFS 1 cam 165 heads, and AOD. Put this motor to get her and have been running it around town for about 2 months. Now when driving it the ten gage sits in the middle to slightly below. The issue is when at idle for more than 15 or 20 mins gage goes up and pushes coolant into over flow tank but doesn’t boil. I changed the radiator to a 2 core and replaced the fan clutch. Still the same. Doesn’t have the usual head gasket signs so I block tested and all good. No leaks any ware and hold pressure. Cap too is good. T-stay is a 195 and new. Is it a flow issue? Do I need to upgrade water pump or change t- stat. Or head gasket? Heats up quickly with ac on as well also when it cools fluid returns back to radiator. Been driving this car around for 2 months and it just started this. Any help would be appreciated thanks

No under drives on it, got a high volume water pump coming, will see what happens
I will have to agree on fluid flow. Even with no t- stat I can squeeze the top hose flat with no effort

Well thanks for all your help, installed the new water pump from Gmb, not sure what makes it high looks the same as old one even the impellers, and 192 t stat. It cured the over flow problem in the overflow tank. But still gets a little warm if it idles more than 20 mins with ac off. Put a new motor craft cap on and and seems to be ok now with a/c off. A/ c on at idle it takes a good 15 mins to creep up to around ware the “o” is on normal and quickly comes down when in motion. Normal cruising and traffic lights sits solid at between the M and the A. I can live with that for now lol. My 89 ran a bit warm with the AOD in it too so I guess the extra drag on the engine may have something to do with it. Thanks to you all out there for the help, been hitting up this form for years. Now finally decided to join