C4 issue

[trei75bronco]

ave a c4 in my bronco i am pretty sure its going out.
1000 miles or less on it
Manual standard pattern transgo
Stock converter according to shop
Derale fan cooler combo
Band m deep sum pan
Raybestos reds clutches

C5 case with c4 internals

Temps have always been on the high side temp taken in pan. 190to 250

Pegged at 250 today
Shuttering from time totime when coming to stop
Power is terrible
Hard ro get above 2k rpm in 3rd
Fluid coming out dipstick tune under hard acceleration
Feels gritty when off gas and coasting ( maybe atlas)

Anyone have help?

The previous owner said he had heating problems with it could it be a case problem