My Altered with Y power uses a Powerglide behind the Y engine with a homemade ½” thick aluminum adapter plate. Because the top two bolt holes on the Y coincide very closely to the top two bolt holes on the scrub bellhousing pattern, the Powerglide transmission on my adapter is clocked approximately 3° clockwise (looking from the rear) to give those top two mounting holes for the transmission a clean area for the mounting studs. It’s clockwise rather than counter clock wise so that the shifter arm in the transmission is ‘up’ rather than ‘down’.
I’ve also used the Powerglide trannies successfully in a rash or other race cars with good results. Good parts and good assembly practices make these the transmission of choice in lightweight drag vehicles. For my ’57 race car I am using a C4 so I can take advantage of the lower first gear but I’m still having to use an adapter so that the C4 mates up to the Y engine while using a SFI rated flywheel.
Here’s the link to thread that shows a picture of the adapter fabbed up for my ’57 that is using a C4 tranny. This uses the same basic fabrication techniques as the adapter for the Powerglide.
And here’s a link to where a forum member used the Wilcap adapter and was happy with the results.

Lorena, Texas (South of Waco)