This is on my to-do list.
First I need a little enlightenment from the wisdom community.
It has always bothered me how the AC system pulls down on the vehicle power, thus causing much greater gas consumption.

My father had a big hp Chevy V8 and when the AC was turned on, you could feel the pull down on the motor, likewise with my 1994 S10 V6 4.3L. However my wife has a 2000 Saturn SL1 L4-1.9L SOHC, this car get 41 to 43 mpg on the highway, the air is soooo cold and you can’t hardly tell it affects the engine.

The only thing I can come up with is, the compressor on the Saturn is a rotary compressor and the one on the Blazer is the dinosaur version.

Is there a proper (Rotary ?) compressor for the 134a that fits my Blazer, or if you addressed this problem, what did you do?

 

First, it's all relative. Your dad's big car likely had an A6 which was a boat anchor compared to today's tech but was used on high ticket cars around the world.

It was much better than THIS 'Old Tech':



The R4 which you have was developed later

Now, lets dispel the notion that the Saturn compressor doesnt pull down the engine:

Warm the car up and shut it off, then pull the IAC connector at the throttle body. Start the engine and turn on the AC. I think you'll find it uses some power.

While the Saturn compressor is newer technology, it still is a 'piston' compressor AFAIK.

You are right in that the R4 uses an 'old' technology, a variation of it was used in small displacement engine for many years. I had a similar compressor on my Eighties Mustang 2.3's and they didnt appreciably bog those engines and I really saw very little difference in either 'bog' when it engaged or gas mileage.

Starting in 96 the R4 having been retired, the Blazer uses the same tech as your Saturn, but a larger displacement because it's a 'full size' car for all intents.
Excessive bog also is caused by improper charge or contaminant in system.

If you do want to 'upgrade' all you need do is change everything over to the 96-up configuration.
Not a small job.

 

I agree the Saturn compressor has an effect on the motor, but with the 1.9L engine with little bog on the motor and fantastic gas mileage it's great.

My current AC equipment is still original, so it takes the R12. It's been leaking, thus having to add refrigerant until the spigot was turned off in favor of the 134a.

I've been with no air for a while (which really doesn't bother me, but it bothers my wife) so I'd like to bring it back. Alldata info says the original compressor can handle both the 134a as well as the R12. Naturally it requires some retro, but if the compressor is good it doesn't have to be replaced. Mine works, or did, but there are obvious leak problems.

I felt like my Chevy compressor, like my dad’s, bogged the engine too much and was astounded with the performance of the Saturn 1.9L. I didn’t want to unnecessarily get something that I would be unhappy with, that is unless it is the only option. As you suggest it isn't.

So where do I look to find out the involvement of an upgrade to a ’96 configeration.

Edit: My compressor is a R4

 

First you go to Rockauto or similar and look up every part of your system And the equiv 96

Pretty sure at least the evap coil {heater box} is the same. Write them down.

Then find someone with 96 up and take plenty pictures of everything that's different. One thing will be a sure problem is Accessory brackets for engine. IIRC, almost everything moves

And junkyard is your source for most stuff.. except:
Accumulator - New {cheap anyway}
Orifice tube
Compressor - AC Delco or Four Seasons rebuilds.
Condensor coil.. not sure. If it needs different one maybe you should get new. I know there was a prob with them on 90's Suburbans but havent seen that on here.

 

Thanks for the knowledgeable insight. You have given me a lot to explore in determining the action I embark on.