Mark 8 96-98 gas shocks or are air shocks computer /compressor standard?

[BILLBOATS]

I have a set of t bird gas shocks that are said to replace old shocks according to some members in the past. requires some modicacition average difficult. Today I see arnott sells the rear air shocks with air nipple and electrical connecter for the rear of the marks and they cost 322.00 for 1 shock while the non air t bird shock is sold as non air adjustable. are 35.00 thru carid each. I bought them 3 years ago and they are box new. The marks have air bag on the rears along with a shock absorber. Puzzled why arnott sell a air shock for 322.00 when air bag and a gas shock are factory .Are air bag and non air controlled shock standard for the 96 mk 8 since new.??? Are the air electric shock sold by arnott by arniott a new way around replacing the air bag thus the shock is electric over air??? costing 322.00 each plus tax and shipping? What does the board know? Thanks in advance to mk 8 owners and lincolns of every vintage