I'm looking forward to seeing a picture of your machine.
While your machine may handle the thicker fabric, generally these old machine can handle it for a while, at least, but were not made for it on a regular basis. I don't know what machine to recommend for sewing mostly heavy fabrics.
As a side note, many machines are listed for sale for way more than what they can actually sell them for. It amazes me what some people will pay for machines on either end of the scale. Some very nice machines are actually given for free.