Here is a list of Bos for sale in the US.
V35s,
A36s,
You mention 400nm trips weekly. Fuel at both ends? If so tip tanks not required as a normal Bo will do 750nm easy...more LOP.
Turbonormalising?
Turbulence can clearly be an issue in NZ due terrain and strong winds so far south. Icing levels too.
Turbonormalising will give you the chance to get above both those more often than not. It also gives you a significant gross weight increase and moves the CofG in a V35 about 1.5in forward so you would find that, for instance, a TN V35b with a decent yaw damper might actually become a realistic 4 seater + bags + enough fuel to safely fly 400nm even without tip tanks.
The gross weight increases seem to be very model specific but a little poke around suggested that some models of A36 could be as much as 450lbs.
TN is anything but cheap...about US$50k to add it onto an existing engine
A Gamispec TNIO550b is about US$75k...it'd be one HELL of a great engine but
It might be cheaper to buy an aeroplane that is already thusly equiped and let the previous owner cop the capital loss on the TN mod....Unless you really are going to keep the aeroplane a very long time then it can make sense to buy a older aircraft that is good in all other respects and spend the cubic $ to make it as you want it to be.
As an example...there are only 2 TN A36s in that link above...the cheaper of the two was an '81 model they are asking USD245k odd for...the other a 98ish at 400k++. Non of the V35s are advertised as TN and I could find any that were...BUT....take this one with a nearly run out engine argue em down another 15k and drop a Gamispec TNIO550 in it for about US$200k total.
http://www.aso.com/i.aso3/aircraft_v...xxxregionid=-1
Make no mistake...many people would say that that % of the value of the aeroplane spent forward of the firewall is lunacy but you're going to be spending money on an engine overhaul anyway so you're really only talking about the incremental cost of the TN and the extra bits and bobs that make it Gami spec...porting/balancing/polishing Millenium cylinders etc.
If you intend to keep the aeroplane long term it is probably worth doing...it wouldn't be if you were likely to want a twin in a few years.
I've gotta say that if I was in the market for a V35 the 76 model above would be near the top of any list...everything about it is impressive (already has a yaw damper for starters) except the engine. It doesn't say so but it would likely be an IO520BB and it has 500hrs left to
recommended TBO. Now it might be owned by a really carefull and knowledgable pilot and happily fly on to, or beyond TBO (the general condition of the aircraft suggests a very particular owner who doesn't skimp) or it might not.
If I REALLY wanted or needed TN I would be tempted to buy this aeroplane (assuming it is as represented- i.e. georgous) for say 15k less than asking price and see what sort of an exchange I could get for the engine on a GAMIspec TNIO550b. The prop is a Blac Mac by the look of it so compatable with the 550b. The air con is a bit of a worry...they are a pain and it would be likely to contribute to CofG problems...I'd have it removed and sell it.
You could end up with an absolutely FANTASTIC aeroplane for less than US$200k.
You could do all the above with a similar mid 70s A36...I think you'd end up with a better aeroplane for a little more money but A36s do attract a premium.
Or you could spend 2+ times the $ on a new Cirrus
I really cannot get my head around that
