If you like plate blocks and enjoy them as a hobby and are "not in it for the money", and the quantities are low enough that you can make use the overage for postage, then go for it.
HOWEVER, keep in mind that virtually no modern plate blocks are worth even full face value in any quantity and you will find many dealers actually use them as postage just to get rid of them.
I did an "unscientific" quick survey on
ebay listings for "discount postage plate blocks" and came up with ten listings as shown below:

It just goes to prove that most sellers are accepting from 50% to 80% of face value for their offerings -- with some sellers even including free shipping. It's not a lucrative market.
Also keep in mind that if you're talking about a number of stamps from the 1970s, that was the time when plate number strips of 10, 12 or 20 stamps were prevalent, which may not lend itself well to just collecting a single stamp with a plate number.