Follow up:
On the way down we ended up turning off of 75 at Sherman over to Gainsville, then took Hwy. 51 south to I-20 at Weatherford. Took I-20 west to 16. both 51 and 16 were pretty good 2 lane roads (mostly 70 MPH). They were doing bridge work in Llano which held us up about 5 minutes.
Coming back we 281 north from Johnson City to I-20. The only roadwork was about 300 yards of shoulder work. No problem. Took 51 back to Gainsville. Driving time was the same either way within a couple of minutes.
Thanks for all of the input.