Some good advice here but some is opinion, my 2V Clevo heads were done by HARRIS (who have done all my work for many years) in Ozzy Park, $780, all new quality 4V valves and springs, stellite exhaust seats, valve heights all the same and springs at same tension, 2 needed shims and 6 needed a skim as the seats were way to high compared to the rest, dags knocked off chambers and ports. These have been on my 51 for 4 years now, If its a SUPER hot day and I've only got 95 in the tank it runs like crap in traffic, other than that its crisp and doesn't detonate but recurving the dizzy took a bit to get right to get it really nice.
The ally heads are a nice addition, I drove my mates Mustang with iron heads then we swapped AFD's onto it with no other changes and, in my opinion, it did go better, it seemed more flexible through the power band as in it was wider, started to come on a little earlier and accelerated harder than before.
My engine is a basically stock 2 bolt with a 4MA crank and the bottom end was balanced and rods and flat top pistons weigh matched and everything remachined including, and this is important with Clevo's, the lifter bores and cam tunnel (your cam should spin freely once installed without the lifters in, otherwise the tunnel is off or the bearings aren't sitting perfectly square in their bores and will need hand scraping to get them to the point of allowing the cam to be free of drag.), I now have phosper bronze lifter bore sleeves in mine as it was so far out, this also doubles as a oil flow restrictor device to keep the crank and cam fed and not fill up your rocker covers with oil during a sustained burst of revs, (you can specify how much you want to restrict flow, 10%/20% etc) my kit is from the USA, I bought a few as I have multiple Clevos and will fit them at each rebuild from now on.
I have a 5500 limiter on my MSD, that's enough for my use, the old dunger still sees off the 317kW commies easily, they just don't get it, almost the same power in an old XD ute that weighs a fair bit less (like 400Kg +) LoL.