Assuming the new one retains the re-popped AK wheels, both kits are a very good start. However; the cab, fenders, and firewall were modified for the 1973 Street Rods issue. That, and the injectors went away. In addition, the dual exhaust was truncated.
For Lesney's A-Venger, the new tree with the crude blower set-up obliterated the cavities for the distinctive nose piece, and the tonneau cover. In addition, the sidepipes were obliterated to put the stock 29 front axle on the chrome tree (what was Lesney thinking?) I may well have missed a thing or two, but that, in a nutshell is what's missing. I covered the complete history of the kit in My Vintage Workbench column in Model Cars Magazine issue 216, including photos of Harold Perry's gorgeous build.
AMT made some nice "implement" tires around 1965 that were included for some of their gasser options, that would get the front end lower to the ground. I think Chuck Larson did that with his build years ago.
Having compared the old and new tool kits, there is scarcely anything I'd use from the new one, except the front tires, and possibly the suspension. I used a set of the new tool front tires flipped inside out on my Dusty Rose Model A roadster, and they also presumably could work on the front of old tool Ala Kart. Using them inside out allows use of the larger old tool wheels, and you simply paint the whitewalls on the now outer side. That's probably what I'll do when I get around to building one.
Another alternative, though pricey these days, is the super nice Danbury Mint Ala Kart.
