74 vette A/C R12 => R134a help

[ssb]

Needing some expert advise on installing a new ac system on my 74.
The car: coupe, 454 BB stroked to 489 ci. New DeWitt aluminum rad, dual fans, dual fan PCM control, new 74 evaporator, modified evaporator case to accept a later model, 1" longer fan; installed all new seals in the evaporator case; sealed all of the factory ductwork connections using 3M high density foam, insulated all of the floor and firewall with double aluminum sided jute under the factory insulation on the new carpet.

I am planning to use R134a and have been looking at the new Sanden 507 compressor, and also am looking to buy a new style horizontal condensor, not using the old snake style.
I have called a few new AC companies, and they tell me that unless I install ALL of their components, including their duct work and hangy down evaporator case, into the car, they will not warrant the cooling system . . . okay . . . and I'm in no mood to remove all the work I have accoplished thus far.

First: Should I or do I need to replace the existing VIR? I understand generally how it works, but since I am swapping over to R134 should I replace it? Why or why not. Is the Sanden 507 the right selection?

Second: If the VIR must go, what is the best system/combination of parts? One with an expansion valve/drier, or an orfice tube/accumulator? Types prefered? Is there any system other than VIR that does not cycle? Can the newer Sandens live without cycling or must they cycle? Cycling pros/cons?

Third: Has anyone out there been able to successfully keep the factory evaporator case and evaporator, 74 style, and upgrade from R12 to R134 and enjoy stellar performance?

Lastly: Please let me know if I have not asked the right question, and feel free to answer that question!
Southern gal needs to be COOL!!!

[c4c5specialist]

HI there,
When you retrofit R134a, the entire FACTORY system can be used with great results.

I have done many and using factory parts, simply evacuating the system, replacing all the Orings on the connections, using PAG oil, replacing the receiver/dryer and then recharging the system yields equivilant performance from the R12 type system.

VIR, to what are you refering???? Aftermarket systems are basic, the factory system will work VERY WELL if correctly retrofitted.

Feel free to ask any further questions.

Allthebest, c4c5