That's a pretty good deal - just make sure it fits. I had a heck of a time getting a 26R battery to sit square on my OEM battery tray - ended up going back to the group 35 battery. The 26R will fit without the spacer, but rocks around a bit, due to the shape of the OEM tray and the supporting bracket underneath.
Same brand we have in the truck - we haven't run into any issues yet. I was a fan of those AGM gel batteries back in the past. Great power density, maintenance free, unbelievably heavy. Paid between $150-$200 for those batteries - great battery, but what they cost, they didn't have that many advantages over the cheaper batteries for just a starter battery. Once you get into some specialized tasks - where you might benefit from a deep cycle or even multiple batteries, it is a matter of diminishing returns, IMO.
Yeah, Diehard - they were a decent battery, made originally by Johnson Control Sytems then by Champion labs (Exide Labs) - but some people found out later than Exide was binning the batteries, the better ones they sold under their premium brand name, the seconds or lightly defective ones were sold to Sears (hence that rash of batteries that died very quickly). After that debacle - they switched back to Johnson Control System - which also makes the following: Duralast, Interstate, Diehard, Everstart, Prostart, Kirkland, Advance Auto Silver - also happened to be the OEM for Ford, Chrysler, Honda, Nissan, Isuzu and even Toyota TrueStart batteries. Doesn't mean that all are the same quality - many of the requirements are set by the end vendor - so an Autozone Duralast battery has different specs than an Advance Autoparts Silver battery. Interstate Mega-Trons will have different plate to electrolyte ratios compared to a Walmart Everstart Maxx battery.