If that an original BB truck, I'd keep the BB in there. It's also an anniversary truck which is neat. Should take of picture of SPID and post it. It's the tag located on the backside of the glove box door.
Also being that it's a long bed, I wouldn't lower (much). Here's an example of what I think looks nice. It's a 70 lwb, with a 402/400 set up.
http://i263.photobucket.com/albums/ii140/70cst/CSTNewShoes.jpg
http://i263.photobucket.com/albums/ii140/70cst/70cst8-1-3-12016.jpg