You need something like these ....
The old workshop press we had years ago had loads of plates for the job.......
may be worth a head round the door at a local "old time" garage
Don't look like Busa pistons ..more like aftermarket that have had valve pockets machined deeper.....and as Ian said sharp and thin edges are a NO NO...
Still onwards and upwards Figs show promise..........Every Days a Skool Day
I posted a reply in your other thread Lock up clutch help.......
Have a look at the Definitive guide to clutch conversions by Lee Workman Lee Workmans Clutch Stuff
Does your press not have the narrow / thin plate,s that you can put behind the gear and press on the shaft to move it
i have complete gearboxes if your desperate , but poss not cheapest solution