I’m 65 and have SEP IRA contributions from 2017 that will become long term on April 12th. Can I use it to fund 2018 by doing a w/d and then contributing back for 2018?

I’m sure this is rather unorthodox but that’s why I need your help. I’m wondering if rather than sell stock shares and pay tax on the cap gains (over cost basis) in 2020, I withdraw funds from an existing SEP IRA to fund 2018 SEP contribution? In order to fund an IRA and a SEP IRA and still pay taxes against pension and our soc security, I have to amass the funds by selling stock.  The SEP contribution will be about $2500 and that’s sitting in a money market in the sep (that becomes long term 4/12). I’m wondering if it’s better to just use that than sell anything. Any thoughts?