Ditto to all the above...
Under the windshield gasket, the dash is welded to the cowling...dozens of spot welds!
Like they guys said, it can be done, but it's a pain !
But go ahead and cuss the SOBs that hacked your existing dash...I've seen darn few that escaped "violation" !
I was lucky with my Grandad's '54 Chevy dash...they modified the center section where the radio mounts, to accomodate a '52 Chevy car radio...the original radio "delete"plate hides most of the carnage.
My former '51 AD was not so lucky - previous owners took a torch and carved a hole out of the dash (right through the stainless trim !) to fit something, then later pulled it back out, and boogered some sheetmetal into the hole...wuz UGH-ly!