Why do I only have 2ed and reverse

IF you can't find the other gears 'at all' by using the shifter ... It's internal transmission damage and will have to be removed for repair or replacement... IF you got the skills, you can remove the shifter and shift the transmission with a screwdriver or other similar tool just to convince yourself it needs to come out but that's up to you... Most likely failed shift forks but that's just a guess... Either way it can't be fixed externaly.. It's been a while since I worked on one of these but if you have to replace it and are looking for one.. , the Dodge D-50 trucks are same thing I'm pretty sure... Salvage yard will know for certain.. Good luck!