OK sounds 310s are a good option, what about the Aztec?
What is the order of recommendation?
Depends on your mission and what sort of twin you're looking for.
Mission would be to take one or twice a year a 1,000 mile trip over open water and have safety margin in IFR condition.
Bascially more a travel plane than a 50mile fun plane
I wouldn't consider any twin to be a "50 mile fun plane" except maybe an Apache. Other than that, any twin should be able to do at least 150 knots... And any of them can get you across a bunch of water.
What are the difference from 310 to 340 to 337?
Let me rephrase, is a 340 a pressurized 310 and this adds a ton more cost at annual?
And requires another endorsement?
As
@Zeldman said, it's not exactly a pressurized 310 - It's cabin class with an airstair door and has some other differences. However, in terms of what you can carry, systems, etc it's fair to call it a pressurized 310. It's what happens when a 310 and a 414 love each other very, very much...
The pressurization itself doesn't add much cost, but a lot of other things about it can get a lot more expensive because of the pressurization. I've been told that it's a good idea to be comfortable with writing a $100,000 check once every 10 years or so with a pressurized cabin class twin. You might get lucky if you don't own it the year that happens, or it might happen the day after you buy the plane... And you don't get to choose which of those it is. It's certainly a risk.
Also, FWIW, my airplane partner and I were looking at 340s... But I recently started flying TBMs for work, and I've got to say, it really made me appreciate my Mooney. The flight levels are boring! Also, the Mooney gets me places very quickly, faster than a lot of light twins and right in the range of the best normally aspirated ones - But it's so cheap to operate that I can still take it out just to screw around once in a while and not worry about how much it costs. That's not the case with something like a 340, which will cost you $400-$500 an hour easy.
Here's the questions I would say are important to answer to help us help you choose the right twin:
1) What is your purchase budget, what is your annual operating budget, and how many hours/miles do you expect to fly?
2) How much payload weight do you need to be able to carry, and for what distance?
3) Are you going to be based at a field with any significant obstructions, or above a couple thousand feet MSL?
4) Are you going to be going in and out of the Rockies on a regular basis?
5) Are you and/or any of your regular passengers, uh, "big boned"? IE, do you need to have something significantly wider than most singles?
Damn that’s pretty. I didn’t know those existed.
Well, a few of them do anyway.
115 built, according to Wikipedia, a small fraction of Twinkies, 310s, etc.
https://en.wikipedia.org/wiki/Gulfstream_American_GA-7_Cougar
Didn’t Ron have one for awhile?
Yes. I had to look to verify, but it seems he had it from 2000-2005.
Chatted a bit with my mechanic, his first choice would be a Twin Commanche followed by a Baron.
He is not a big fan of 310's as he expects annuals in the $5k- $10k range.
Yeah, Twin Comanches can have $5K-$10K annuals too. So can Barons - In fact, it's almost a certainty with them as well. I generally expect about $5K on the Mooney even, and it's just a baby (1997).
I think maybe he's afraid of the 310's gear rigging procedure.
His own plane is a Grumman (Single), but I think a Cougar may be hard to find and then hard to upgrade Avionics (lack of STC's)?
Definitely hard-ish to find. Right now, there's one for sale in the UK that's a solid "Meh" but importing aircraft can be very expensive; there's also a project one for sale. If you're looking for an easy ownership experience, you don't want either of them.
As far as mods, I don't think that'll be too big of a problem. I just looked it up for giggles, and the GA-7 (TC number A17SO) is on the AML for the Garmin GTN series, JPI 960, Aspen, G5, G500 TXi, etc. Now, you'll almost certainly never get any of the modern autopilots that have been coming out recently, but there is an STC for the KFC-200 so you might be able to snag a used one and add it if you get one not so equipped.
But, it is still a pretty rare bird.