Hi itchybird,
First, always consider the problems with the Whizzer are the direct input of Joe Lin. The mushroom lifters are a perfect example. I sent several sets of American made lifters as a guide to what needed to be made. Of course the lifters he made were not even close to correct. First of all the American versions were hardened, his were very soft. Secondly the one I sent were lighter than the stock lifters, his weigh almost twice as much. Next I made the "mushroom" approx 1/8" in height, whereas his version was over 1/4", and in some cases the "mushroom" hit the bottom of the lifter bore at high RPMs. Many times the lifters won't fit in the case because the O.D. varies greatly, and some were even tapered. I have been re-working the Tiawan version and they have been doing well. I cut the base down, drill out the center and harden the lifter [$25.00 labor].
Both of your motors have the better camshaft, therefore no need to buy another camshaft, just replace lifters.
I do have the aluminum manifolds in stock, however he even managed to mess them up in the process. NONE of them are drilled correctly and the intake port is usually off as much as 1/4". When I sent the information concerning the manifold it was approx. 9/16" to 5/8" long, and in the process he managed to make it too long [effects mid range torque and top end].
It seems like no matter what, he had to make things differently to claim it was his design.
If one of your motors has the aluminum manifold, chances are it will also have the mushroom lifters and they can be modified to get the job done.
It is very important not to run a NE motor for a extended period unless it has the mushroom lifters. The very first NE motors had WC-1 lifters, and they quickly ate the camshaft lobes [total dustruction of the camshaft]. Instead of using the correct lifters [mushroom], he simply heated the lifters to make them soft. The soft lifters prolonged the life of the camshaft, however several issues became a major problem. One problem was the "softened" lifters wore quickly and became much shorter causing the clearance to change and the motor would run poorly. Another problem was the base of the lifters flared out, pieces broke off and found their way to the bearing in the motor case. Can you say "major damage"? The shorter lifters and the increased clearance would cause the lifters to slam against the valve stem and flare the bottom of the valve stem.
Good news! Once the motors are modified they do well and become very durable. Once the minor issues are addressed, the motor will give you a lot of trouble free service.
One serious problem to consider on the very late motors is the condition of the aluminum in the cylinder. They weren't tempered correctly and the head bolt threads "shear". If the cylinder is re-cured before a lot of miles it can be fixed. If a lot of miles are put on the motor prior to the re-curing process it makes it next to impossible to maintain the thread structure. You can solve this problem on your own if needed. Remove the valves, springs, retainer washers, and "C" clips from the cylinder. Place the cylinder in an oven @350 degrees for 3 hours, let cool gradually. This process will soften the aluminum and stop the threads from "shearing".
Hope this information helps.
Have fun,
(jk Jim 
)