Questions about 87 HB (Dash, Notch, Etc.)

I just recently drove from IL, close to St. Louis, down to a little town 2 hours south of Nashville, TN for a 1987 Nissan Hard body Pickup. I am new to HBs but I've always been a big fan. This truck has been lowered, was previously bagged in the front but they put the brackets in upside down, and they screwed me with it cause halfway back, in the middle of KY the tranny went out and I had to drive back in 4th gear. My main concern right now though, seeing as I'm getting the tranny fixed soon is how to swap the dash out with a Nissan car. I have seen it done, I think with a Silvia dash, but I was wondering what dashes I could use and how to get the gauges and things to work afterwards. I was also wondering if anyone had experience with dropping them to tell me if I had to notch the frame somehow in the front in order to get it to sit 20's. Any help would be greatly appreciated cause I am new to Nissan HBs.