The compression is the issue here. A stock 80's truck motor is going to have toilet bowl compression. Probably 8:1 or less. I wouldn't go any higher than this:
Xtreme Energy 218/224 Hydraulic Roller Cam for Chrysler 273-360
If you can get the compression above 9:1 then consider 224/230 cam. No higher than that with a factory converter.
If parts get mismatched you'll have an absolute dog. Learned this the hard way in my early 20's.
As to roller vs flat tappet, I'll never run a flat tappet again. Machine work on a lot of lifter faces are causing cams to wipe out. Been a problem for a while.
And you have a block that'll run a roller without having to use expensive retrofit rollers. Be sure to make sure the springs match and pushrods are the correct length.