Morning Lyn, the 302 was basically a 327 with a 283 crank, 202 /160 valved heads, 11 to 1 compression, high winding small block actually started in `67 in the camaro`s although rare in the first year ( none were badged as such in 67/68 ) continued in 69/70 as the famed Z/28, the 350 block started in 67 used as general production better torque, the 302 was brought into play for the SCCT racing, so many had to be built as standard production to qualify for racing.
And the 307 was a member of the 283 family, with a diameter 3.875" bore. The 307 was produced from 68-73. By putting a 3.25" stroke 327 crank in a 3.875" bore 283 block you get a 307 engine. Nearly 40 years ago, I bought a 68 GMC 3/4-ton pickup with a 307. At 95,000 miles, it had a serious oil consumption issue; burned it, leaked it, and added a little to the coolant too. I pulled it out and dropped in a junkyard 327, which was a good engine for the balance of my ownership of that truck.
The 302 is a 4 inch bore block and a 3 inch stroke. Its a high RPM engine. Early rodders used a small journal 327 block and a 283 crank. The factory 302,s that came on Camaros used a large journal 350 or 327 block. At least some of them did.