I came across a home with the roof rafters spaced at 48" with horizontal braces about every 2 ft. the home was built in the 40’s and had a ridge board. the pitch was around 4 and 12. anyone seen this before?
Yes. The horizontal members you saw are called purlins.
I see it all the time. I have built a ton of commercial building this way and a few homes. Purlins set at 16" or 24" O/C.
Without being there or any pictures I obviously can’t tell if it is built correctly.
they could be 5’ or more apart. it depends on the rafter and purlin material type and size as well as the decking/ sheeting material type and size
It sounds to me more like blocking rather than purlins.
Pictures of differences between blocking and purlins. For me anyway the internet can be helpful sometimes.
I agree with Rob. What size are the rafters and how far do they span and what size are the purlins and what size is the decking/sheathing? 
Pictures are always helpful.