Buying FTE cars just for the axles seems like a waste so here is a simple solution if you haven’t got a source for the pins. On eBay search “nickel plated bank pins”. 1 1/4” #20 is what you want. They slide right into the brass tubes and fit perfectly into the hot wheel tires/wheels. The pins do not slide into the aluminum tubes but could be taped in for a crimp/glue free axel solution.
For older hot wheels the 3/4” #12 pins from Walmart are a perfect fit. Brand I found works is Dritz