To answer your specific question about income, the answer is: about $20,000 (or a little less) in yearly income put you in the top 10% of income earners in the United States in 1970. This information is provided by this US Census Document (PDF page 13, labeled as page 11, table 1, document entitled "Household Money Income in 1975 and Selected Social and Economic Characteristics of Households").
The census data also has a breakdown by race of head of household, and note that this is household income and not individual income (so 2 income households are included in this data, though 2-income families were more rare then than today). Median income was around $9,000 per year at this time, so a little more than double the average family would put you in the top 10%. There was also much less inequality in both income and wealth during this time period as compared to now.
To compare this to the 2014 census, and you'll need a household income over $150,000 to get into the top 10%. Note that this link also shows 1970 information, but everything is inflation adjusted to make it more easily comparable dollar-for-dollar - sort of.
What Was "One Million Dollars" In 1970? About $100,000 (by income -sort of)
If you are a top-10% earner with a yearly income of $150,000 now, 1 million bucks is a little less than 7 years of income. If we apply this multiple to 1970s income of $20,000 per year, that means that 7 years of income is $140,000.
So I suppose in a very rough estimate sort of way, you could say that $100,000 in 1970 is kind of like $1,000,000 today - about 7 years of income if you are just barely making enough to be in the top 10% of wage earners.
Why Not Use Inflation?
The problem with inflation is it is generally defined in terms of a specific "market basket" of consumer goods, to try to compare general buying power over time. The problem is that this is a really rough, problematic estimate, because things change in price relative to each other over time. JoeTaxpayer makes a very good point about interest rates and houses, and another example is consumer electronics. Not only are today's electronics actually cheaper than they use to be, but they are difficult to compare at all because they are more powerful and useful than ever before. Similarly, cars are safer, have less emissions, and are more fuel efficient - so a simple inflation calculation based on macroeconomic changes can provide a very distorted and inaccurate picture.
It's up to you if you think an income-based estimate is more helpful to you in actual 1970s dollar amounts, or if you'd prefer to think costs and use measures of inflation as your guide.
Side Note: Income Inequality Has Changed a Lot Since 1970
In 1970, half of households made more than $10,000 a year and only 4% made over $25,000 (more than 2.5X as much as the median). In 2014 about half of households make over $50,000 a year, while 5% make over $200,000 a year (more than 4X as much as the median). These numbers are all rounded to convenient numbers, but the reason I mention this is that the difference in the top 10% of wage earners now compared to the "average" American is far greater (in absolute dollar terms) than it was during the 1970s. There is also a greater proportion of the population now that earns more than 2.5X as much as the median - about 11% of households in 2014 - which suggests perceptions of what is "a lot of money" will vary more now than it would have in 1970.
In 1970 our top-10% family needed around 7 years to make $100,000, while the median family needed 14 years to make that much. In 2014 the top-10% family needs around 7 years to earn a million, yet the median family needs more than 20 years to earn the same amount.