If it were me, I would remove the center radio grill and work through the hole. Getting under that dash is a pretty awful job. On my 38 Chev Master, I can lie across the front seat and gaze up at the dash. It is a treat to work under that one.

1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed

My Chevy Master 4 Door is on the Road!