This subject comes up about every month and I have a first hand opinion on it from my 54 project, so here is my opinion.
The camaro subframe can be made to work on AD trucks but it is too wide by a smidgen. If you lower the truck you will have a tire/fender clearance problem UNLESS you use wheels with significant backspacing. This brings it own problems in inner fender clearances IF you plan to run wide meat on the rims. Some who do the Camaro/Firebird subframe swap also change out the control arms with aftermarket versions which remove the fender clearance issues. However, IF you go that route you have already spent close to or more than a model specific IFS kit would cost. Again it can be done but is not the perfect solution.
Regarding the 73-8? front suspension swap, this is a total abomination for AD trucks in that is is much too wide. If you like that look then fine, it is your truck but you will not be able to lower the front end to the point where your tires will fit under the fender lip with out again utilizing rims with severe backspacing. Some who use this suspension system also take about three inches out of the middle to solve this problem but that invites other "issues" such as engine mounting, new brake lines, modifying the centerlink, etc, etc. That can be fun if you like that kind of work.
Another option is using a G-Body subframe (78-88 Monte Carlo, Regal, Cutlass, Grand Prix). This suspension matches up well with the original track width but also has a host of fabrication issues (First hand experience here) the major one being a severe core support/steering box interference. This swap is NOT recommended for someone not familar with welding, fabrication or for people with lots of hair as you will be pulling it out.
If any of the sub-frame methods are not performed correctly it can ruin a project and be a complete waste of time, effort and most importantly...CASH.
THE BEST SOLUTION FOR AD SERIES FRONT SUSPENSION UPGRADE IS...
an IFS kit. This will give you a proven system which will be safe, solid and will ADD VALUE to your project. The other options may work but will not have the value adder that an IFS kit will give your project.
For the $1,500 or so that an IFS kit will run you, it really is cost effective when you look at the cost of purchasing the other options and the time and money spent to fabrication/repair them into service. This is one of the biggest "lessons learned" I have from my project. Hindsight tells me I would have been further along if I had used a kit.
In my opinion though, the subframe options are very viable for the 55-59 series trucks as few if any of the interference issues are present.
The 73-up front suspension is just plain wrong for AD trucks.
Agree with this or not, that is my $0.02.
Edit 1: Here is a link to a current thread from a bolter dealing with the problem of the 73-up suspension now.
https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/360079#Post360079Edit 2: Another option is the S-10 frame swap but the cost of that is equal to or greater than an IFS when all is said and done UNLESS you fabrication all the body mounts yourself.
Edit 3: I just re-read your original question and will add that the 68 camaro sub-frame with the rear steering IS a good option for the AD truck. The 1st gen camaro and the early Novas 68-72 have that type of sub-frame. The track width is good for the AD and the only real problem you will face is header clearence on the left side caused by the steering box. You may be able to find headers to solve the problem though. If you do not have the cash for an IFS I would recommend the rear steer sub-frame as the next best option. Good luck.
