The 340 6 BBL used the 340 4/BBL cam.
Wiki had a good write up:
https://en.wikipedia.org/wiki/Chrysler_LA_engine"340 V8
Mopar 340 cu in (5.6 L) Small Block
In the mid-1960s, Chrysler decided to adapt the 318 cu in (5.2 L) small block V8 into a lightweight, high output engine equally suited for drag strip or street performance use. Its block was bored out to 4.04 in (102.6 mm) but 3.31 in (84.1 mm) stroke left unchanged, resulting in the 340 cu in (5.6 L) engine. Anticipating higher loads resulting from racing operation, the engineers fitted a forged shot peened steel crankshaft instead of the cast nodular iron unit used in the 318. This also included shot peened and forged pushrods, connecting rods and pistons. A 4-barrel carburetor was mated to a high-rise, dual plane intake manifold feeding high-flow cylinder heads that are still considered among the best of that era.[citation needed] Its big ports used 2.02 in (51 mm) intake and 1.60 in (41 mm) exhaust valves. An aggressive cam was fitted to take advantage of the much better breathing top end. The 1968 4-speed cars got an even hotter cam, but it was discontinued for 1969, where both automatic and manual cars shared the same cam. The engine was equipped with hydraulic lifters and two bolt main bearing caps, leading some to initially underestimate the 340's potential. The 1968-'71 340's compression ratio was 10.5:1, placing it near the limit of what was possible on pump gasoline during that era. The 340 also used additional heavy-duty parts, such as a double-row roller timing chain and sump-mounted windage tray. Power output was officially stated as 275 hp (205 kW) gross for the 4 barrel.
In 1970, Chrysler offered a special Six-Pack version of the 340 with triple 2-barrel carburetors rated at 290 hp (216 kW) gross that was specific to Challenger TA and Cuda AAR models. This version featured a heavy duty short block with additional webbing to allow for aftermarket installed 4 bolt main bearing caps. The application-specific cylinder heads featured relocated intake pushrod passages with offset rocker arms that allowed the pushrods to be moved away from the intake ports, which could improve airflow if the pushrod-clearance "hump" was ground away from the intake port by the end user. An aluminum intake manifold mounted three Holley carburetors, and a dual points ignition system was fitted.
The combination of rising gasoline prices and insurance company crackdown on high-performance vehicles saw the relatively expensive 340 detuned and phased out. It remained a high performance engine through 1971, but was de-tuned in 1972 with the introduction of low compression (8.5:1) small valve heads, and by mid-year, a cast nodular iron crankshaft, and a variety of other emissions related changes. For the 1974 model year it was replaced by the 360 cu in (5.9 L) engine."
