First, sorry for your loss.
Second, putting aside for a minute that it was your brother’s truck, the question of lifting or lowering (in this case leaving it low), is always a highly subjective question. Some people have really strong feelings for or against lifting and lowering. Personally, I’ve always had appreciation for both schools of thought. I lifted my Choptop (89 Bronco II) and I lowered my 00 green Ranger. I love both trucks, they are both a lot of fun. My F-150 is lifted when compared to stock trucks of its vintage but it’s really more heavy duty suspension and bigger tires. I’m looking at going with even bigger tires on the rebuild but maybe not really lifting it because it’s supposed to be a work rig and when you need a ladder to reach the ladder rack it becomes a little more awkward.
I try to build my vehicles for a particular purpose. I like a lot of different stuff and styles. Personally, considering that truck is already lowered, I’d be inclined to finish it out, make it nice, maybe build it for better performance if there’s anything left to do on that side of things. It would be a huge amount of work to build it the other direction and a big expense. Be easier to pick up a stock truck or someone’s abandoned project to build into a desert runner. But ultimately it’s your decision and we shouldn’t influence that too much.