During CV boredom, I decided I'd "modded" my last factory guitar and decided to learn to build partscasters and just make exactly what I thought I wanted. Anyway, 5 years later and I now own 4 partscaster teles... It seems I'd rather play Legos with them than play them.
What I've learned-
1) I don't like humbuckers in a telecaster (or a strat). I've tried and tried. Not PAFs, not slightly over or under-wound, not split... I just can't get that tone out of a telecaster HB like I can with a LP and there's always that tele twang coloring the distortion. And if I take the pains to make a tele sound like a LP, it's no longer anything that remotely resembles a tele, tone-wise. I can put lesser HB's in a LP and make it sound better than better humbuckers in the tele, if that makes sense.
2) I like P90s in a tele and I like Filter'Trons in a tele. However, I found that those p/u configs yield a very limited 1-trick pony-type tone. Therefore, I prefer the spank of a slightly overwound (~7.5-8k), true tele bridge over a P90 bridge, but I like a vintage P90 in the neck. Now, if you want something close to a HB sound from a tele-style bridge p/u, they make those, too. The DiMarzio Chopper (mini HB) and the Area-T "Hot" (Stacked/noiseless SC) are both very hot and supposed to be tone-modeled to replicate a PAF HB when distorted, but can be dialed back down to spanky levels when needed.
3) I have a storage box full of pickups I've bought and tried over the years. P90s might be the hardest to choose. IDK why, but it seems they're the most prone to having frequency spike variances, meaning 2 pickups from different manufacturers with nearly identical specs will sound completely different, where one will be mellow or mid-rang-honky and the other an icepick to the ear. Need to know what you like and what you want. Lots of research.
4) If you really want a Tele with p90s, or especially if you want a mix of p/us (p90 +Tele bridge) I'd buy it that way. Mainly b/c you'll play hell trying to match poalrity and wind direction of a normal tele p/u and a P90, they're allover the place (even inside the same manufacturer) b/c they don't get paired that often. Also, wiring can be a headache b/c some p90s want a 330+k pot w/o sounding muddy... and that value is too high for a tele bridge w/o bleeding it off with a resistor. But, if you want to mod or build, Seymour Duncan has this p/u setup on lockdown. While the DiMarzio Twang King bridge is my idea of the epitome of tele sound, SD's LaBrea is really, really close. But SD's "Antiquity" P90s are golden, imo.
5) There is always the HB-shaped p90s, too. Not really p90s, but they come close. Fat p90s. I have a set of Tonerider Rebel 90s in another LP. They're a unique tone and they take dirt better than a tru p90.
6) Have you considered a JazzMaster? Those pickups are very p90-like - less grit, more bottom and more articulate. My daughter has the 60's Classic Vibe Squier JM and it's pretty nice. You could put real Fender p/us in one for arounf $100 and still be close the the $500 mark total investment.
This is my P90 Tele build. It does blues just fine. The p90 gets very sweet about 3/4 of the way up the neck. It currently has Wilkinson p/us in it b/c they sound that good. The Wilkinsons put to shame a lot of p/us that cost 2-3 times as much.
