I have over size product that cost way more to ship than my standard product. Is there a way to have a "Contact Us" label and for "OVERSIZE" product and still show it's still in-stock with out having the "ADD TO CART" label on the product page? I plan on sending the customer a PayPal invoice with the actual cost of shipping for oversize product..
Alternate template is solution for it more you can read here https://shopify.dev/tutorials/customize-theme-create-alternate-templates
Once you do it replace 'add to cart' button with contact form or MailChimp a/to your need.