You don’t have to buy Bitcoin to get exposure to the upside potential (and downside) in Bitcoin swings. You can buy stocks that are involved in Bitcoin mining and/or have a large percentage of their net worth in Bitcoin. Other stocks are involved in blockchain technology.For example, this week Tesla (TSLA) announced it bought $1.5 billion in Bitcoin and would accept payment in Bitcoin. The company has about $20 billion in cash so this won’t make a huge difference in terms of its market value, which is $783 billion, as of Feb. 12.However, analysts suspect a good number of companies will follow Tesla’s lead. They may begin to treat it as a legitimate treasury asset. CNBC reported that Wall Street is inching closer to accepting Bitcoin as an investment asset class.Moreover, Mastercard (MA) said this week it would support some cryptos on its network this year. In addition, the Bank of New York Mellon (BNY) said it plans to transfer, store and issue the digital assets.Until that happens, here are four stocks where Bitcoin and cryptocurrency is a major portion of their assets or business.Overstock.com, the e-commerce company, started venturing into blockchain and cryptocurrency as early as 2014 under its former CEO. Today it is still one of the few online retailers, along with Square, and PayPal that accept cryptos as payment.Overstock has a subsidiary called tZero which is a crypto exchange. It is registered as or is applying to become a money transmitter (or its equivalent) in many states. tZero is actually a division under its wholly-owned subsidiary named Medici Ventures. Medici Ventures also has minority investments in various blockchain-related companies.That’s all very interesting. But here is the bottom line. So far Overstock doesn’t seem to have made any money in crypto exchanges or currency. There is no line…