Reusing existing hardwood with some additional stuff

[rarara]

I am planning on moving some existing hardwood from one room to another, and I will need to supplement it with approx 10 more square metres (I am thinking trying to get reclaimed since it will be cheaper and probably more of an age to what I have). Eventually this room will get a light sand and varnish, so existing finish isn't important. Stuff I currently have is 20mm thick, beech (possibly maple!) and approx 85mm wide. So my questions is:

Should the T+G part of any other 20mm hardwood (obviously that is a colour match) be a perfect fit?

 

[big-all]

very unlikely
but if the boards are the same size you can just remove the tongue from the transition area
assuming you group the planks to different halves

 

[rarara]

the T+G is a fairly essential component in terms of reducing noise in our property, so would rather keep it.

perhaps the only option is to buy a batch for the whole floor unless I can get a match. i want to keep the price down though so trying to avoid that scenario

 

[big-all]

screw some 3x1" underneath one plank between the floor timbers to give a lip for the other board to sit on
or even 12mm ply will do if its airborne noise suppression through gaps

you could always take an offcut off board round the yards just make sure your offcut is representative off the largest amount off boards

also you are unlikely to get nearer than a close approximation with the colour more likely a bad match