I towed with 250/200 and an s467.7. it towed awesome,never hazed at idle and if I let it would have surely killed my stock 350k e4od (it's still alive with regular service btw).
Imo you have to have 4.10 gears to tow much. I had lots of issues with towing with 3.55s original to my truck. After the 4.10s I could tow at Interstate speed with cruise on and not kick out of Od in southern indiana.
To run a big set of stix you have to imo have enough turbo,gears,and fuel. Sure you can buy 400/400 but when you turn them down to a spit amount why have the big injectiors even? Unpopular opinion is 90% of the 7.3 have way larger than ever utilized injectors for absolutely no reason.Your stock connecting rods will fail before you actually use all the fuel you think you need. I killed my original short block . When I pulled it apart the rod that broke showed fatigue and there was another cracked half way thru just wating for its evacuation sequence. I also found severe main cap fretting due to main cap walk. If you want to build an engine to use much more fuel than a 160 then this build just got way more expensive .
Me personally,I sold the 250/200s put a good used engine in with some 160s and a gear head tune that tows fine and won't evacuate my crankcase. If I'm being mean to it I can put it in the old 250/200 tow tune and it makes all the boost and smoke I could ever need.Yes I am still running the s367.7 and it spools just great and I'm happier with my combo. I never put the head studs,valve springs,pushrods,t500 back in even

Save your money and just buy some 160s or spend that big money.
I'm NOT the first to have this but you can sure be the next .
If you want to see the fatigue pics of my broken rod I can share also.

 

I always tell folks about your rod failure, believe he had them too @kameronth with a few bent. @427 fordman stated he did pure beef rods for that reason, due to fatigue and the build.

Curious the limit for a reliable, upgraded fairly stock 7.3 Maybe 325-350rwhp? Which I guess around 650-700rwtq.

 

That is a real good question that I'm not sure we could answer deftinitively. I just hate seeing people buy huge injectors,spend a bunch of money and kill their engine while having them turned down in the tune all for no more than what a 160 would do. We need to have much more air than most have with less fuel than everyone thinks they need. Yes we need more than stock inj can provide. I'm going to stop now because I could type another page of personal theory but nobody really wants to read that lol

 

And "stainlesstroker95" Gabe killed his I'd dare say fatigue rod with 238/80 and an s366. He doesn't beat on it and it failed just cruising down the highway to work.

 

To be honest with you I'd be worried about the rods with anything much more than a chip on stock sticks. They are 30 years old. Fatigue sets in after a while. Heck, I had 160/0 stage ones and I hit over 40 lbs of boost. I blew my original motor up with those. Broke a piston. Rods survived but I wasn't trying my luck with them in my new build.

 

I agree with you! I need to honestly concentrate some effort on a real engine build. That's why I never put head studs,vs,pushrods in this engine. Idk my ultimate plan tho with family demands,other projects etc that it'll be anytime soon. I just keep it on the gear head small tow tune and hope for the best by not beating on it.