I would think a battery is a battery and it would work just fine as long as the heavy cranking power is there when needed.
Like the other post indicated however you may have to get an BATTERY POST adapter to fit you truck engine battery cables which you can find at the local auto parts stores and PEPBOYs...
The other problems may be with the truck electronics when the alternator is being told to charge your deep cycle battery. Deep cycle batteries used with RV's like to live with 14.4VDC for charging and 13.6VDC when maintaining their charge. Hopefully your truck alternator system does something around the same settings. i.e. it would not be a good thing if the truck electronics would always send 15VDC (or more) charging voltage to the deep cycle battery when being charged. There is also a desulfation battery mode for deep cycle batteries that occurs every 15 hours or so for about 15 minutes associated with RV DEEP CYCLE batteries. Not sure this would be an issue or not. I notice others on here have stated they have used the deep cycle batteries with the truck start location without issues.
Myself I probably would NOT do this for any long term use. One of my biggest rules when camping is NEVER do anything to the truck as that is you life line for getting back home. I would however do it in a heart beat if I lost my truck start battery when camping and needed to get home... That would fall under a PLAN-B situation.
I would also caution on disconnecting the truck start battery for any length of time. The truck has several computers involved with operating your truck electronics and when the start battery is disconnected for any length of time all of the computers will reset to some state. When you re-connect the truck start battery it is suppose to re-learn all of the required settings. In my case when I had my truck start battery disconnected for just 24 hours the truck engine idle did not return to normal and my truck would not run at idle speed. It would die on me. I tried to raise the idle speed manually but the new trucks apparently don't allow you to do this anymore. It has to be done electronically. I ended up taking my Ford back in for service to have the computers reset on their diagnostic machine which cost me around $90. Won't do that again haha...
Roy and Carolyn
I claim Horse Creek Country in Southern Ill - Momabear is from North Texas
We live in King George VA
RETIRED DOD DOAF DON CONTRACTOR Electronics Tech 42YRS
"We're burning daylight" - John Wayne
2008 STARCRAFT 14RT OFF-ROAD POPUP with PD9260C and three 85AH 12VDC batteries
2010 F150 FX4 5.4 GAS with 3.73 gears - Super Cab - Towing Package - 2KW Honda EU2000i Gen
K9PHT (since 1957) 146.52Mhz
"We always have a PLAN B"