4ages are a well sorted bit of gear. They used them in a race class in the u.s. called formula atlantic engines. These where super modified, and from memory spun over 11000rpm!
You can also build gun engines from factory parts because of all the different versions of the 4a. i built one a few years back for a mate of mine which consisted of (from memory) the ae92 block (which has oil squirters to cool the bottoms of the pistons and lube the walls and has as many ribs as the 4agze block), 20v black top crank( light and best balanced ans i think is steel from memory) 20v silver top rods ae92 pistons, and 16v small port head. Gives like 11:1 comp ratio, using factory bits. And after the flogging this one we built cops, i can vouch for them bein bullet proof. revs to 8900 easily, and with some more head and vavle work(which are standard at the moment) and different cams, i reckon she would spin upto 10000! Problem is runnin that throught the t50 gearbox is pretty #OOPS# house unless you have 50 gearboxs and enjoy changin them or u can afford the w series dellow bellhousing