TapRackBang
Cheaper Than Diamonds
I never had the money to buy the Heath Kit stuff in the 70's & 80's, but I love building kits like that.
We are living in the heyday of kit building. There are more kits to do more things from more people for less money than ever before, IMHO.
Just a small sampling of kit makers and parts suppliers:
https://www.electronics123.com/
https://www.qrpkits.com/
https://qrp-labs.com/
https://qrpguys.com/
https://www.adafruit.com/
https://www.sparkfun.com/