It's good to know that you have great interest in Toyota motors, but you got all the facts a bit upside down there. Firstly 4A-G is the official code for the engine itself - designated as performance model for 1.6L belt driven engine by Toyota & Yamaha - and Blacktop on the other hand is the "NON OFFICIAL" name for 4A-GE Twin Cam 20 which was produced between 1994 to 2000 - Commonly found in JDM AE111 Corollas and Sprinters. The earlier 1991-1994 version is called Silvertop - of course comes with Silver Colour head commonly found in Corollas and Sprinters too - they all are 4A-G. THEY ALL BELONG TO THE GREAT 4A family - even the locally assembled 4A-FE is from that linage.
If you need more info on this, just spend a few hours at
www.club4ag.com , read the Tech Info section carefully and you will know the whole story. Comprende!