I would take a different approach for this size lathe, and it all comes down to availability of motors in your location and shipping costs to your location. Some/most of the US eBay vendors do not have shipping to Canada, those that do are expensive and you have customs/import duty. You would need to contact them as to costs. I agree that a TEFC or better yet TENV motor would be the best option. If you can get a inverter/vector motor (i.e. one that must be run off of a VFD) you will get a wider operating range and pretty much full torque down to 0 RPM. I would go with a 3 Hp motor for several reasons, the stock motor was 3.6, you will not notice any difference, shipping will be less expensive, 3 Hp VFD's with single phase input are readily available at reasonable cost. Move up to 5 Hp and you have doubled or tripled you VFD/install costs. You lathe has multiple speeds if you really need to gear it down, but I have a similar sized lathe with a 3 Hp and the motor doesn't flinch and I take it down to 20 Hz. If you can go with a smaller motor pulley size you can optimize these types of motors toward their higher RPM's and get the benefit of the mechanical ratio advantage and a wider speed range. A 6 pole motor is going to be a bigger frame size and offer little if any noticeable performance advantage in this setting. Once again if you can find a 6 pole or 4 pole 5 Hp cheap then it would be a decent option, but factor in the additional costs when going to a higher Hp motor.
The motor below would be my recommendation, if you can get it shipped to canada, otherwise you might go with local motor houses. Most motors will do just fine as a replacement with the voltage spec. you are looking at, chances are the stock motor was a TEFC. This motor can only be run off of a VFD.
3HP Marathon Motor, 182TC, TVB182THTS8028EPL Blue MAX Y527, 230/460V 1.9A 540... | eBay
As far as VFD's well it going to come down to cost and basic features, as you do not need anything high tech for this application. You will require an external braking resistor to aid in stopping and you need to understand that you cannot use a VFD as a power source for the lathe, it must be directly connected to the motor. You bypass the contactors and such, and you should not directly wire the VFD control inputs to your controls. You need some basic control system for safety reasons, you have a foot brake if used you need to send a free run command to the VFD when using it. If this is not a 24/7 industrial setting I think you can get by just fine with mid priced VFD's such as the Teco E510, Hiatchi WJ200, there are a few Fuji models, and sure if you can get a Nidec / Control-Techniques drives at similar cost go for it. I just prefer to keep things simple at this level. Teco E510 is probably the easiest to setup and understand. Cannot recommend any of their lessor model or the Chinese generic VFD's.
This vendor might ship to Canada, or there may be a source in Canada, more to give you pricing.
Purchase 3 HP VFD, 230 Volts, NEMA 1/IP20, Teco, E510-203-H-U at Dealers Industrial
Hitachi, WJ200-022SF, 3 HP, Variable Frequency Drive 230 Volt, 1 Phase Input, IP20, at Dealers Industrial