any ideas for a easy lift for my Cub snowthrower

You could put caster wheels behind the blower on short parallel lift arms. Then the long lift handle would have a mechanical advantage of about 4:1. You would have to rig up a whole system though and even though it would work, for the fabricating that would take you might as well go with a hydraulic lift kit. I have the same problem with my blower, and am trying to get a stock hydro lift of epay.

Well they did make a eletric lift for your Tractor. Here is what it looks like
The older Hydraulic lift will fit as well. I think I paid $275 for the electric lift with electric lift Undercarriage when my actuator dies I will replace it with a more modern actuator even though I can still rebuild the one I have The modern one's are just faster. The same undercarriage will work for the older Hydraulic lift which can be found for about $450 on ebay You just have to unbolt the drive shaft to put the Belt on for the Hydraulic lift Pump since the sheave is already on the tractor for the Belt:thThumbsU

If you have less money, more time and some even a moderate level of fabrication skills do this:
Some tractors will be easier to do this than others depending on design and shapes. Some tractors will need holes drilled through fenders and maybe some other parts.
With some thick flat steel or maybe some wide and heavy angle iron, build a "U" shaped mini frame a little bit wider than the tractors frame and at least 18" long. Make the corners square and not rounded like the bottom of the letter "U". Drill through both ends of the U and mount to the tractors rear frame section in the lowest part and mount to tractor. Get some heavy cable and at least 2 good pulleys. Steel plumbing pipe might be needed in some sections to route the cable through so it doesn't rub on something functional or easily breakable. Mount first pulley up on one side of the rear part of the frame. Mount 2nd pulley ahead of it next to the hood but well above the snowblower. The cable goes from the "U" shaped frame up through a pulley, along the side of the tractors frame and up to 2nd pulley and down to snowblower. Add weights to the "U" braket and you have a counter weight for the snowblower. You will need a little bit less weight on the back than what the snowblower weighs. Its a bit low tech but is essentially its a pivoting rear counterweight for the snowblower that also adds weight to the rear of the tractor. I literally just thought of this after reading this post. Hopefully someone on here can understand what I'm describing and make a diagram of this and post it here.
Another possible way of doing this is to just run the cable up to the arm of the lift lever on the tractor to reduce your effort. Add or reduce weight on the "U" frame as needed.

I use a gas spring shock off of a Chevy blazer back hatch I think. All I did was hook it up to the top u bolt on the lift bracket and the other end i made a little piece of angle iron with two holes drilled on each side and bolted it to my starter generator. It works real well for my qa-42 snowthrower and my rototiller. If you can see it in the photo. Ill get some better up close pictures of it if wont them.