I'm interested in building an adjustable electronic load as per Figure 6 of the apps note here: http://cds.linear.com/docs/en/application-note/an104f.pdf
Which ADI amplifiers would be the best match to replace the LT1210 and LT1006?
For the LT1006, I think the ADA4638-1 is an excellent part as replacement. ADA4638-1 is a high voltage, high precision, and zero-drift amplifier with rail-to-rail output. It has lower input offset voltage and drift, lower offset current, and higher open-loop gain. ADA4077-2 also has close specifications to LT1006, but comes as a dual.
For the LT1210, ADI currently has no amplifier with a current drive of 1A. However, for this application, I am not sure if A1 needs that much current to drive Q1. AD810 and AD811 are high speed amplifiers with slew rates of 1000V/us and 2500V/us, respectively. They can drive large capacitive loads with some external compensating resistors/capacitors. AD817 and AD825 are both high speed amps with high capacitive load drive, but with lower slew rates.
I hope this helps.