I had a Viking 6440 that I got for free and I had it rebuilt by a Viking tech who loves the older machines. It did have a cracked internal cam and was really stuck inside. It cost about $250 to have it like new, but sews like a dream now. I passed the 6440 on to my SIL who needed a tough machine to make dog collars. I found another Viking, a 6020 that went to the same tech for rebuild too. The 6020 is a keeper designated fo my hubby who sews his own gear for his black powder shooting hobby (pre-1840 clothing and gear). I have also pieced on it. The 6000-series are a workhorse with the low gear, but do to be run at least monthly because of the self lubricating bearings. So I would say the vintage Viking would be a great choice if you are prepared to have it gone over by a tech as the cam either has cracked or WILL crack. I couldn't tackle that job by myself but a was fortunate to find a long-time Viking tech about an hour away. Some techs might not know how to work on them or be able to find the parts (there is a good aftermarket cam replacement). A different SIL has a 6440 too and the shop she went to said hers was unrepairable. My brother got the part and did it himself. Hope that helps your selection process!