"O" heads

They are very unique, from a restoration standpoint.

The 'O' heads are technically correct for 1970 340s only and are 2.02 valved in stock form.
On '70 340s there are 4 other castings that are technically correct, BESIDES the 'X' head. They are O, U, Z and 'J' castings.
Some very late '70 340s got 'J' castings that have a 'U' on the underside, some also were 'J' all around, in very late '70 model year.

The 2 original 1970 360s I have seen had 'Z' heads.
The 360 was actually introduced in May of '70 in certain Dodge 4 door hardtops, it was also the debut for the part-throttle kickdown on automatics.
There is actually a TSB out there advising of the '70 360 and the transmission's part-throttle kickdown, which also specifically gets into car line and manufacture numbers.

Mark.