I agree with SM that the most telling thing about your post is that he get's aggressive when you try to voice your wanting to spend more time with him. Spending time with him shouldn't be a fight for you - and this is all early on in the relationship, prior to kids so this could be a big red flag as to your needs being met further on in the relationship. Try planning things ahead of time, and if that doesn't work it might be something that you need to discuss with a marriage counselor. If he's says no to a therapist for you both, it means that he's not truly appreciative of what he's got and truly invested in keeping it. As far as the truck goes, there's only so much that can be done, and it could probably be counted on 10 fingers as to what he could possibly do to it. (so his obsession will peter out when he's finished the truck). Have you got any hobbies that you do together? like camping or hiking? He sounds like he likes to be busy, so why not pick something for you both to get involved in (bowling league with friends?) Also, you've mentioned his hobbies, and also that you help him, but what about you? Do you have hobbies? It might help a whole lot for you to pick a couple few things for yourself to get into and may be one answer as to you and he having that in common? (hobbies and special interests). It might be that it would help you (if you haven't already) to join a gym and /or find some friends to walk with regularly. That might make it so when you do get together , you're both more appreciative of the time you spend.
Argh. Sorry! That is frustrating. I mean, you want someone to enjoy their hobbies and all but when you become like a hobby widow . . . that's not good. And that he gets irritated about it when you try to discuss is also very frustrating. He should be open to communication that includes hearing your feelings! Men are tricky. Not to be sexist but that is my opinion. LOL
So, two things that come to mind are to A. what about being proactive and setting up something ahead of time that you'd like to do. I know it would be nice if he had the idea to do it but until he smartens up about this . . . you have to take the bull by the horns. You can tell him 2 or 3 days ahead of time that you planned X for he and you to do. Or tell him that you really want to go to this movie and it is at X time on Saturday, so he needs to be ready by 45 minutes before that time so you guys can go and get there in time. Just start scheduling things during those days leaving an occasional one untouched for him to obsess over hobbies. B. A bigger problem is his not allowing you to open up dialogue about how you feel. Feeling ignored and neglected is important to discuss and if he can compromise. You can acknowledge that his hobbies are important to him and you don't want to take those away but just would like to have more of his attention too.
The fear is that if you two go further in the relationship and he stays this way, what if you have kids? Is he going to leave you to do all the child care while he works on his truck? Is he going to miss things because of his truck with the kids? Is he going to have no time with you as a couple because he ONLY does his hobby and kids things?
So, being able to talk about your boundaries and your feelings with a life partner if it is supposed to be that eventually is essential. And he needs to be more open to that. Perhaps your approach made him feel on the defense which is easy to have happen. So, think about wording and tone and if that has anything to do with his reaction.
Let us know what you think!