I replaced mine with period but new speakers all round - my car is a cab and suffers from the lack of rear parcel shelf mounting options. I used new (1980's - still boxed and sealed) JBLs in the rear side panels, Pioneers new the same in the doors. I have the seperate speakers tweeter and woofer but removed the old tweeters and carefully cut the old tweeter basket, then modified the new one with some help from a strong two part based glue, fixed the new tweeter in the old basket, allowed to go off, and then remounted using original tweeter grill - same with the Woofers only they came with identical to factory standard grills (apart from a non visible Pioneer logo that is down inside the door tray) - and I have new clear sound that looks all original.
Shop around and check before you buy that you can modify both the old and new speaker baskets to be able to re-use the grills, unless you can get matching grills, but the max power generation of speaker styles that are out there are not my bag.
My old original speakers were torn to shreds, but I guess thats from years of over use with the hood down.
Good luck with it