There are obviously a variety of factors to look at with any car purchase besides just the make and year. That said, and keeping in mind that I have not seen any of these cars, I am inclined to lean toward the 1987 300D or the 1992 190E. The W123 chassis of the 1983 300D has proven to be durable, and 130k is relatively low mileage for such a car, but $7k sounds a little pricey. I checked kbb.com, and the trade-in value for such a car in excellent condition in my location (Denver, CO) is only $1650, so $7k sounds excessive.
It has been said time and time again that the W124 chassis is your best buy in a used MB, period. I'm not sure I totally agree, but the W124 chassis is definitely a good bet. Additionally, the Mercedes diesel is one of the most long lasted engines ever put into a passenger vehicle. For that reason I would choose the 87 300D over the 87 300E.
The 190E may be a good choice, and the asking price seems reasonable. The manual transmission is a good feature when you consider long term reliability, and the car has lower mileage. I would seriously look at the 87 300D or the 92 190E.
1976 300D (W115) - 330K and still going (sort of)
1991 300D 2.5 Turbo - Sold at 221K
1983 280SEL - Sold at 206K
1981 300SD - Sold at 232K