Given the numbers involved, your Roth conversion will be roughly 40% nontaxable and 60% taxable. about 60% of your basis in nondeductible traditional IRA contributions remaining in your traditional IRAs to be applied to future traditional IRA distributions and Roth conversions. Nothing is permitted to be done to change these tax consequences.
In 2024, it would seem to be sensible to make your full nondeductible traditional IRA contribution for 2024 and convert all of your traditional IRA money to Roth. Pay the tax on the pre-tax money now and let it grow, with the growth being tax-free instead of tax-deferred once the requirements for qualified distributions from your Roth IRAs have been met.
