I replaced the OEM 34 gallon tank in my GMC with the TransferFlow 56 gallon inline one. Had it done by a local dealer from their website. Unless you can raise the truck up enough to work under it (not lying on your back) and are familiar with the fuel system hookups, having it done may be the way to go. That and you need to have the OEM tank almost empty before starting, even if someone else does it, due to the weight and possible spillage. Took them two days to complete it since they couldn't get started until the afternoon I dropped it off. They were a small shop.
Overall, I've been very satisfied with it. Only hiccup is the DIC in my 2009 GMC can't be programmed to show the range for the added capacity, but it's no biggie. The mpg readings are still valid and I know how much fuel is in the tank because the gage still reads it correctly. So, if the range on the DIC says I'm about to run dry, I know there's still 22 gallons of fuel left.