Brian, on the rear of the 990 will be a phono socket which will have a closure on Tx this is used to put the linear in operate via the connector on the back of the KW1000, however you will need to check in the manual what current draw the 990 will take. You may have to build a switching cct with a higher current rating. Those old amplifiers can take as much as 0.5A to go into Tx.
You will also need to connect the ALC line of the 990 into the ALC input of the KW1000.
Also make sure you read about tuning valved amplifiers, you can destroy the valves if you over drive them when not at resonance.
Might be an idea to find an old boy who has used valve amplifiers in the past to give you a hand, a 60 min job can take hours:)
