Hi RyanH,
I understand the difficulty of proving the costs of improvements. Of course, any documentation would be helpful, but few people would have saved receipts for that many years. I recommend that you work with your father to develop a list of the improvements with approximate dates and estimated costs. This will go a long way to providing a logical explanation for how you determined the basis when you eventually sell the home.
Having concrete proof of the basis is not necessary when you must report the sale of the home. But in the unlikely event you are audited, the more information you have the better.the outcome.
Hope this helps!
