I rode Arlington to Waco a few years back with LSR, I'll see if I can find their route.  Maybe on of the active Rando's on the board has newer info.

I have driven through there several times in the past 2 months.  Just north of Hillsboro the access roads are quite discontinuous, almost completely non-existent as you get in towards the I-35E/W merger.  You may be able to take detours through the closest small town but that will add significant mileage to your ride.  There's also a LOT of construction between Hillsboro and Waco (mostly around West) where access roads are pretty broken up by large work vehicles.  I personally would not attempt a direct route via I-35.  Back roads are a better bet IMO, but I don't have a suggested path for you...

Thanks. Yeah, roads just get worse and worse in Tx. I was thinking 833 out of waco if heading to ft worth up to where you have to work your way through the little stuff. 833 maybe isn't too bad, or 308 if heading to Dallas, though maybe that route maybe isn't as good.

281 is problematic as a bike route. There is a massive amount of traffic on it for as small a road as much of it is. There are decent shoulders on much of it but the density and speed of traffic gets very wearisome and the area a little south of Blanco is quite dangerous, imo. Once you get up past Burnet and especially Lampasas it's not a bad route but I couldn't recommend it between Austin and S.A. I tried a number of n-s routes in Central Tx west of I35 and frankly, the I-35 access road was about 10x easier and safer. Hwy 16 has some great parts but north of Fred'burg has a tiny shoulder with a lot of traffic. I rode that stretch when checking out the route for the first HC600 and told them I wouldn't ride it again. I suggested 2323 from Llano, which they agreed upon.
 
I've ridden 317 north of Belton to near Crawford and that's not too bad. haven't tried 56 from there up through Whitney to 174 where I'd try cutting across to Cleburne maybe, or over to 144 to Glen Rose. That stretch looked pretty nice iirc and was wanting to try that but never did.
 
South of Austin I've ridden several of the n-s routes. Hunter rd, s of San Marcos was a bit of a problem with traffic last time. used to be a great route but not a few years ago. On Google maps it looks like they might have redone the worst stretch of it but it's a little hard to tell. I've ridden Seguin Rd and 90 all the way to Flatonia (then headed up 609 through La Grange then over through Brenhan/Navasota/Conroe, etc and most of that was fairly decent. Have taken a few different routes through Lockhart but never headed north towards Austin from there. i still say that S. Congress is the best way to get through the south side of the Austin area then I went up Trinity/Duval/Speedway or sometimes just scooted over on Guadalupe if traffic wasn't too high. Then up Georgian or hopped over onto Lamar. South/Central Round Rock was problematic but they were redoing Grimes Road east of I35 last time and that might be a great way to go. From Georgetown to Waco on I35 access was a breeze except going through Temple and there's about a half-mile stretch I think somewhere around Eddy where you have to jump over on the I35 shoulder.  Don't know what 308 on the east side of I35 around Hillsboro is like.