Unfortunately, Al, it's what Gwyn says.
We own a Bulgarian house and want to move ASAP. Our financial numbers are very similar to yours, with the addition of some remotely earned income (enough to live a decent but frugal life in Bulgaria, but not the UK) I can continue to earn no matter where I live. Buuuuuut, I am having to dream up more and more convoluted schemes that might enable us to move there sooner than 2027, when I can start claiming my OAP and apply for a retirement visa. Because unless one has a LOT of money, just having enough money to support ourselves isn't enough. Over 300,000 EUR for residency by property investment, over 500,000 EUR for residency by investment.
But it's not all negative! There are some possibilities for you. If either of you are doing or already officially retired from a job where you can take early retirement and claim a company pension that is at least equivalent to the Bulgarian minimum wage, you qualify for a retirement visa. It's pension based not age based, and private pensions qualify. Or if you own yourselves or know someone who owns a UK company in good standing (submitted tax returns for at least the past two years with a decent turnover), Trade Representative Overseas could still be an option, though the requirements for that are tightening up quite a bit. The final and worst case scenario is spending 90 days per 180 at the Bulgarian house and the other 90 days per 180 either back in the UK or some other non-EU country like Serbia or Turkey, possibly even owning two houses for the time until official retirement lets you apply for a D visa and residency. Though one thing to think of there is that for someone 12 years from pensionable age, those goalposts might move. It seems possible people of your age may find the UK retirement age becomes 70, not 67.
So it's not impossible to get Bulgarian residency, but it's become far more challenging over the past years, both due to Brexit and to tightened requirements as Bulgaria try to get full Schengen. Be wary of advice (Gwyn, JimJ, and other wise members of this forum excepted!) from those already living in Bulgaria, unless they made the move recently. Unfortunately Facebook groups, YouTube vids, estate agents trying to sell you a house, and people who moved under previous immigration rules, can make it sound far simpler than it currently is.