I have 152,000 on car, owned since new and it still runs great but it now takes a little longer to start and plugs have never been changed. Pulled plugs and they are Denso SK20R11 and the gap on them are .040mm.
If I look online for the exact plug from Denso it shows gap as .043 and a reach of 19mm (3/4").

I find the same info on Rock Auto for their alternate number Denso 3297.

When I measure from edge of gasket to tip of plug it measures 1" (25.4)
Is it OK to get these plugs and just make sure the reach is no more than the 1" as I worry about total length as it may touch piston and keep the gap at .043mm. Just trying to be safe.

 

Denso 3297 is a SK20R11

The Rockauto site lists the "Reach" of the plug as 19mm.

Spark plug Reach is the distance from the seating point of the threads (top of threads) and the bottom of the threads. Reach does not include the distance of the exposed electrode or extended metal shell that is not threaded.

Only measure the length of the threaded area of the spark plug and you should get 19mm.

As to the gap distance, you can re-gap but would not worry about it.