I'm using TD3 steel heel receivers very successfully on TD1 bindings, 5 years of daily carving during the ski season and I've had zero problems with them (and a huge improvement over the aluminum receivers).
It's not the hole spacing that's the problem but the bolt size and the fact that the receiver needs to be shimmed up a bit to make the boot level so everything engages and releases properly. I used the smaller bolt size of the TD3 (6mm), a stainless nylock nut and stainless washer underneath the binding plate, and a short piece of heatshrink tubing around the bolt to (hopefully) protect the M8 threads in the plate. The bolts are labeled "A2-70 THE", so they're a marine grade stainless, M6 x 1mm x 25mm flat hex with a 90 degree shoulder angle, similar to a McMaster-Carr 93395A363. I'm not sure where I ordered mine from, maybe Fastenall. Another source is this: https://www.amazon.com/10-M6-Stainless-Countersunk-MonsterBolts/dp/B078YYDZ34?th=1
The shims are 1/8" aluminum stock with a hole drilled to allow the bolt to pass, and some super thin double-sided tape to hold them aligned to the plate. You can see them under each side of the receiver in the pics below.