Here’s a link to a past thread that has a picture of a lifter tool specific for Y lifter installation. Although this tool was originally designed to install the lifters with the engine in the car, it should work really well with an engine upside down and on an engine stand.
http://forums.y-blocksforever.com/Topic29290.aspx
Chuck. If you need to borrow this tool, just give a shout and I’ll send it your way.