The 401k + traditional IRA act the same way, so only the collective asset allocation (rather than the per-account asset allocation) matters. Just put the funds where they are cheapest (assuming there aren't any funky front-end/back end loads or fees to worry about).
You have $75k * 85% + $54k * 45% = $88K in US equity. Your 401k is $75K. Therefore, your 401k should be 100% US equity and the other $13K should go in your IRA. Your IRA should hold all the bonds and international.
That's for your current assets. Next we have to figure out the allocation for new contributions.
You didn't say what your desired asset allocation would be (check your Investment Policy Statement and let us know), so for now I'll assume that the AA you have is the AA you want, which means US equities is $88k / $129k = 68%.
You also didn't tell us how much you are contributing to your 401k (only that you're planning to max your IRA), so I'll assume you're already maxing that too, so that's $18K and a yearly combined total of $23.5k. 68% of that is $15980, which means that, considering only contributions, not all of the 401k contributions should be to US equity.
However, you've got excess US equity in your IRA, so you can use that to rebalance: you can set the 401k contribution to 100% US equity, but then exchange $18000 - $15980 = $2020 of the US equity in your IRA for bonds and international.
Neglecting the effects of different rates of return for different asset categories, you should be able to do that for about $2k / $13k = 6 years or so before the percentage of your total assets in your 401k exceeds the percentage of your total asset allocation allocated to US equities and you're forced to put part of your bond fund or international fund (whichever is cheaper) in your 401k.
(The math above obviously varies according to what you want your actual AA and contribution amount to be and investment returns going forward, but it should be useful as a guide.)