This site will be your friend in terms of searching for alternative wheels for a 145 :
https://www.carlsalter.com/wheel_fitments.html
What other mods are you considering?
The easiest wheels to fit would be those from a later 240/740/760/940/960, this should give you a few ideas :
https://accessories.volvocars.com/Le...R_GB_NL_DE.pdf
Other than that you're probably looking at concentric hub adaptors to fit different PCD 5 stud wheels and don't forget the original fitment on 145 was 4.5J x15 wheels shod with 165SR15 tyres. That means to safely go wider, you need spacers and possibly use a different offset so the wheels don't foul the chassis at full lock or the body on full droop of th body.
One of the later Volvo wheels (that you'll find on pg 14 of that Accessories pdf) is the Adhara and that would suit a 145 nicely as it's not dissimilar to the Minilite style alloys popular when the 145 was new.
If you're keeping the original engine (assuming it's a B20) then you could do a lot worse than using Eternal Optimists recipe above - B20B with B20E head and cam, it should give an easy 125-130bhp which might not sound much these days but in a car designed in the late 60s and weighing less than a modern Fiesta, it's still going to be pretty reliable and lively.
If you're thinking of changing the engine, the obvious choice is a B230FT (165bhp turbo) and an M47 gearbox which will keep everything looking factory but you'll need the loom and ECUs to use the injection etc. Also a modified fuel tank. It would be wise to find an early 80s 240 with an M47 to retain the cable speedo drive as well.
Alternatively, if yours is auto it's almost certainly a BW35 box. These later became the AW70 box which just happens to be near identical to the Toyota A340 box usually hung on the back of a 1UZ 4.0 V8 Toyota aka Lexus V8 engine. Yould have to change the extension housing, again for an early 80s 240 AW70 extension housing to regain the cable speedo drive.
Then there's the back axle, if memory serves the B20A 145 had a 4.11:1 diff which is ridiculously low for anything more powerful than the meagre 82bhp that the B20A produced. Higher ratio diffs are certainly available in the 7/9xx models, even up to 3.31:1 in some models, not sure if the same applies to the 240 models but the 140 and early 240 models had narrower back axles than the 7/9xx so a tape measure will be useful.
Brakes could be interesting, if memory serves the fronts were 262mm discs with 4-pot calipers shared with the Rover P6 and Austin Princess (wedge shape) models and the rears were 262mm discs and drums for the handbrake - not much has changed on those over the decades!
Again later 7/9xx models will give the options of 282mm ventilated discs or possibly larger but not without going bigger than 15" on the wheels.
Loads of options available, most depend on your patience, preferences and pockets, depth of.