Tires: Two different sizes 2 sets, tire placard, series tires

Question
I purchased a used 94 olds 88 Royale and it has 2 different sets 250/70r15 and 250/65r15 I believe the 250/65r15 is what belongs on there but for now what size is best for the front and what is best for the back

Answer
George,

On every vehicle sold in the US, there is a sticker – commonly called the tire placard - that lists the original tire size and the proper pressure for that size.  The placard is usually located on a doorpost or in the glove box – but sometimes it is located in the trunk or on the fuel filler door.

BTW, it doesn't matter who makes the tire or what pressure is listed on the tire's sidewall, if the tire size is the same as the placard, then the pressure listed on placard is also appropriate.

According to Tire Guides, your placard ought to say the original tire size was P205/70R15 with an inflation pressure of 30 psi front and rear.

So the 65 series tires are too small and should be removed as soon as possible.  Tires that are too small increase the risk of a load related tire failure, which sometimes has tragic results.