Both of these engines aren't hard to do something with. Each can be raised to roughly 620 Hp at the tires with tuning.
The 435 5EK has the same cylinder packs as a 500 Hp 5EK. The 550 has basically the same cylinder pack with the only difference being the piston crown. The 435 cylinder packs can handle the 620 Hp at the tires without any problems. The only problem with the 5EK 435 uprated to 475 is the turbo is smaller than the 5EK 550 hp turbo.
The 6NZ stock turbo will be small at these power levels for your workload, but will survive for a year or so, if it doesn't already have a million miles on it. After that you're taking a big risk of it going bang. If you were staying 80K and less in gross weights they can last for a few years, before the bang