Late shifting into 4th

[Bugsy]

My 87 GN just had a new engine installed along with a 3200 stall converter , new high friction clutch packs and the governor tweaked to give higher shift points under full throttle . Before this the car shifted normally , now it shifts great 1-2 and 2-3 but revs to almost 4000 rpm before it shifts into 4th under light throttle . As a result it cruises at 50 mph at 3500 rpm which is too high
The TV cable is set right . Any suggestions to get it to shift into 4th at a lower rpm under light throttle ?

 

[SSedan64]

Possibly a sticking/binding valve in the Valvebody. May be a burr or debri/trash.
3-4 Shift Valve or 3-4 Throttle Valve.
#323 / #324 >> http://www.gnttype.org/techarea/transmission/valvebody.html