In something like the Bulldog, which had a +4.75 g limit, the corresponding theoretical level AOB would be 79.7 deg. But it could not sustain a level turn at CLmax and 80 deg AoB.
You need to be as low and as light as possible on the buffet nibble with full power. But above all you need to be taught how to do this safely - and NOT in a non-aerobatic light aicraft.
For the max rate possible turn, you would need to reach the sustained level max rate turn, then allow a descent to build up until you reach +4.75 g on the buffet nibble. I only tried this a couple of times in the Bulldog - it is very difficult and quite tiring. Never try it unless you have received training.
Speed is immaterial - you fly on the buffet nibble with full power. AoA is indicated by the light buffet.
To digress, 'MLTs' (medium level turns) in the Gnat were considered so demanding that there was a safety limit on the number of sorties you were allowed to fly that day. Full power, roll to about 90 deg AoB, pull to 5g then squeeze to 6. All the while looking over your shoulder to tell the instructor how many fingers he was holding up........ The Gnat couldn't sustain a 6g level turn, but the Valley Hunter 'GT6' could sustain a 6g climbing turn at low level!