Just a couple of minor points on this. You may not need an engineer's certificate for a 138 red or 149, but you will almost certainly need it for a 202. In NSW that means: HR brakes, seat-belts, heater/demister, electric 2spd wipers (or single speed at > 45 sweep/min) must be fitted.
Garry's comments are fairly accurate, but I recomend you read the article on fitting a HR F/End on our website at
http://www.fefcholden.org.au/techinfo/tech002.html as there are a couple of other tricks and traps.
hope that helps, RET