As CLD suggests, any 60 watt Sunn head (40 watt head for an early l-40) with any D140 loaded Sunn 115 cab will do a decent Sonic l-40 impersonation. The amps themselves are identical to all the other Sunn bass models of the same configuration.
I use a Sonic l-40 cab for all kinds of things, but it has limitation; namely the porting (combined with the fact that it's rear loaded) won't allow many drivers to actually fit, and while it sounds sweet, the original single D140 runs out of gas pretty quick compared to newer drivers. I find the 200S/l-40 cab combo has similar SPL limitations as my B15N does in live situation. I currently have a K140 in my l-40 cab which helps a little, but a 115S cab is more versatile overall IMO.
This is the cab the CLD has, but his is called a “115V” because it came loaded with a Cerwin Vega driver. By the early 70’s the upgrade drivers were no longer JBL. Sunn had three levels in most cabs; “S” models had Sunn Transducers, “M” models had Sunn Magna driver, and “V” models had Cerwin Vega drivers.
I also have a 215S cab that at one time or another I have loaded just about every bass worthy 15” driver that there is. However, when loaded with D140’s it sounds very similar to my 200S cabs with D140’s, so I personally don’t believe there is any sort of “compromise” tonally using the newer front loaded cabinet (115S,M,V 215S,M,V) instead of the traditional l-40 or 200S cabs.
