As well as incorporating all of the later -200 modifications, the -200 Adv included major wing improvements such as new leading edge flap sequencing, increase in droop of outboard slats, extension of the inboard Krueger Flap (
see flight controls section), to produce a significant increase in lift and a reduction of take-off & approach speeds for better short field performance or an MTOW increase of 2268Kg. Autobrake, improved anti-skid, automatic speedbrake for RTO, automatic performance reserve and even nose-brakes became available. Again, kits were available for existing operators of the -200. With the JT8D-15 at 15,500Lbs the MTOW was now up to 52,390Kgs and MLW 48,534Kgs. These performance improvements increased the service ceiling by 2,000ft to 37,000ft and the maximum cabin differential pressure was increased from 7.5 to 7.8psid to accommodate this.
In 1973 when noise was becoming a factor, the nacelle was acoustically lined by Boeing and P&W swapped one fan stage for two compressor stages in the JT8D-17 while increasing thrust to 16,000Lbs. The JT8D got up to 17,400Lbs thrust on the -17R.
This B-737 was line number 427 so it would incorporate the modifications listed above. It's first flight was in 1975 so as delivered, it would also have the engine update.