Flat towing 2003 Ford Explorer sport trac

We towed a '03 ST 4X4 4.0 V-6 for almost 100,000 miles. The harness & light make it easier as on the '03 no flash was done on ours when installed at the Ford dealer we bought the Sport Trac from in '05 with 15,000 miles on it. The kit was installed in less than 10 minutes and the dealer didn't even know what it was. We gave them the part number and they ordered it in for the day we picked it up. The part at the time was $27 with the "installation" running the price up to about $110. How many miles does your Sport Trac have on it? Ours had 157,000 plus 100,000 towed, not showing. After our fall check up on the Sport Trac last year, on start up our independent mechanic pointed out the timing chains (3) starting to rattle. $3000 to replace just the chains, as the engine had to be pulled, but if they "dropped" $6-7000 for a factory long block, which all of the old parts would be reinstalled. He told us to start "shopping for a new toad in earnest" as this was a problem on that vintage 4.0 V-6. The rattling seemed to start lasting longer each with each start, but then I might have been just a touch paranoid. We bought our current 2014 Flex in Mobile AL about 6 weeks later and had it set up and wired to tow for around $1250. New Blue OX Baseplate, coiled cord to coach, wiring, diodes, Patriot breakaway wiring including cable, adapter brackets Demco to Blue Ox and labor.