IIRC the console work is all from inside the car so you don't have to do much of anything from underneath if the shifter is connected to the shift platform and horizontal shift rod.
When I did my 265 conversion I got a shifter surround from a parts car... but it wouldn't be difficult for someone with modest wood tools and skills to cut the wood to replicate the flat section. I may eventually do this since the fit is not what it oughta be.
For the shifter surround I took some vinyl in a color more or less matching my interior (a sort of tan) and made a conical piece using the wife's sewing machine. Warning: most sewing machines are barely up to piercing two layers of vinyl; your significant other will be majorly PO'd if her machine is outa whack because you overstressed it! I stapled my home-made vinyl surround into place on the wood and at the appropriate elevation, then cut off the tip of the cone for the shifter to poke through. It's starting to deteriorate, many years after I made it but I'm happy it has lasted this long. I'll make another, better one when I need to.
AGLA (Alan Gunn Leather Accessories) used to sell leather shifter surrounds, are then still around?